Okay, so I'll:
1. Generate a hierarchical deterministic wallet using some algorithm. Then import the master public key to an online computer running Electrum. (I assume that the master public key can be used to generate unique public keys deterministically, correct?)

2. Then install Electrum to an offline computer but instead importing the master private key. (which can generate unique private keys for the same public keys? Which when derived gives me the same public keys so to say).

3. On the online computer I make a transaction. I guess I initialize the transaction from the online computer because it needs data from the Blockchain which can't be accessed from an offline machine obviously.

4. Because the private keys only are present on the offline computer I transfer the transaction data (how? - usb, sd?) to the offline computer and there I sign through Electrum somehow. (I'll probably find it by clicking around in the GUI).

5. Then take the signed transaction and broadcast it from the online computer to the blockchain.

Do I understand this correctly? I rather not fuck up with 1000$. (Though I'll prob test with smaller amount and/or testnet first.)
If I print out my mnemonic phrase encrypted with a password I should be all set and I can start transferring money to the first generated public address, right?

Thanks, so basically:

Just storing the private key is fine for Ethereum.

HD wallet for Bitcoin is used because of the unspent transaction thingy requires a ton of addresses if I want to actively send funds? (I think I'll learn about it more tomorrow lol).

Just so I understand correctly: HD wallets use a deterministic algorithm for generating private and public keys. So anyone with access to the seed phrase gets access to all of my wallets? Seems like a bigger brained paper wallet hmm.
All BTC HD-wallets use the same algorithm right? So if I wanted I could just manually calculate all of my private keys in my head even without a computer if I remembered the seed? (that would definitely be boring though).

I guess I'll encrypt the seed phrase with a good password using some algorithm and print QR codes that I then store in a lot of different buildings. Is that ok?
Oh, lets say I want to hodl for a year, can I just run the algorithm once to get my first address and then hold all my funds on that? Then when sending a payment I run the algorithm twice to get a second address and use that as change address, leaving the first one empty but with change in the next and then I continue like that?

Mind sharing how to do this?

That seems very nice indeed. But if I don't care about my payments being anonymized I still can't see why I shouldn't just use the same address.
So you basically come up with a seed yourself and then you run an algorithm on it that deterministically generates keys for you? (So you get "infinite" addresses by only remembering a phrase of words (seed, just like Minecraft!!!!)?

Yes, yes. Ofc. I think of the private key as a kind of user/pass combo for signing transactions on the network from your wallet (stored on the blockchain), correct?

Oh okay, I just assumed that Bitcoin worked kind of the same as Ethereum. I'm very new to crypto, got interested like 2 days ago. I have used Bitcoin before for purchases though.
So on Ethereum it's fine to just store the private key on a paper and use it like a password to the Ethereum network?

Just wondering
"So now you have exposed the private key of the address on the device"
How is this a problem if I use a secure computer, like a BSD without anything on it except a program to send Bitcoin?

"and also created new UTXO on the same address which kills the whole purpose of using paper wallet!"
What does this do (explain like I'm a toddler lol). If the change address is the same as my paper wallet address, won't I just get all the change back to the paper wallet?
I mean paying 100$ and getting 70$ back is for an end-user just like spending 30$, right?

And about hardware wallets. Might get one if you say so

If I hodl on a hardware wallet, is it wise to back up the private key on a paper anyways so if I lose it I still have access to all my funds?
If I buy eth and btc and just hold them on paper until I get a hardware wallet, can I import my keys to the hw wallet or should I just send the funds as normal transactions?

Hi, I'm interested in buying some crypto and I've thought about storing it on paper wallets. Mostly BTC & ETH.
I have 8 different places to store it in so fire/water damage won't be an issue.
I'm just wondering about why I'd need to sweep the whole wallet when sending the btc? From what I understand you basically have a private and public keypair and the private is used for signing payments. I'll encrypt the printed keys with a 30-character password which I remember and only store in my brain (permutation of my master password for everything SUPER important, used similar twice before).

Of course I should discard my wallet if I use it on something like a 24/7 networked Windows machine but I guess my airgapped (except when I send payment) FreeBSD laptop would be fine? I'll only use it for crypto payments. The method of sending will be geth (Ether) and my own tool written in BitcoinJ or btcd for Bitcoin. I'm not worried about being tracked either at all because I'll use this only for hodling/some legit payments.

What I'm asking about is why I should recreate a wallet immediately after making a payment? Seems overkill as long as I use a safe computer.
I'll also only store the private key in a ramdisk so any forensic analysis will be useless.

I'll start pretty small at around $1000 since I'm a student, and I rather not risk more. A hardware based solution seems ok but if it costs 10% of what my total amount is it seems like a waste.

So, what's the point of sweeping?
Example for Ethereum:
1. Store private key in ramdisk & use personal.importRawKey to import it after inputting manually from paper (configured geth to store everything in ramdisk ofc).
2. unlock my account with personal.unlockAccount.
3. send eth with eth.sendTransaction.
4. shut down the computer.
Is there any flaw here that I'm missing? I'll get addresses, gas prices, etc. from another computer because I don't want any web browsers installed on the computer.
I'll use the same principles when sending Bitcoin, any recommendations for simple free software Bitcoin tools like geth? I know how to write my own in BitcoinJ but I'd rather want a stable fool-proof one tbh.