Hello Everyone
I have the private key of an old wallet with a bit of bitcoins (dating back before segwit ~ 2013). The key is completely offline.

What I've done is the following:
- Created an Electrum wallet with the key (old type single key, no seed)
- The public key showing for the wallet matches and I see the transactions for the old key (so far so good).

What I would like to do is:
- Install Electrum on another internet enabled computer, downloading the blockchain and creating a wallet (like above) using the. public key.
- This should allow me to create unsigned transactions (?) which I would then transfer over to the offline computer to be signed, transfer the signed transaction back and publish it.

My question is:
- Are there any issue using the "old style wallet"?
- If I only use parts of the funds, is there any issue with the the rest "remaining" on the old key (can the "return" amount be sent to the old key)?
- Are there any other risks with this legacy approach? (excluding either computer being compromised)

My concerns are (generic concerns without any data to back them up):
- That for whatever reason the transaction would not be accepted
- If a "chunk" is sent exceeding the amount of the transaction, the return amount wouldn't be correctly returned
- I couldn't use the same key pair again

I highly appreciate you feedback

Best regards
Richard