I know these are a lot of questions but any advice is greatly appreciated, this forum has been extremely helpful for a noob that has been in the space for about 4 months now. Thanks!
I will try to help you.
I think the main problem with your strategy is that you have already traced what will happen in the next few months:
Altcoin season, then you take profits in USD, then it comes a bear market, you will put in blockfi.....
You need to consider different scenarios, as we don't know if we are even going to have an altseason like before, or even a so hard bear market. Are you ready for a different scenario like a Bitcoin bull run and altcoins losing even more value?
1. When I start to take profits from my altcoins do I just sell them on the exchange for dollars and then buy stablecoins with that? Or do I somehow trade the alts for stables? Does is matter since selling or trading them are taxed for capital gains regardless?
Doesn't make a difference. But you can take your profits in bitcoin. I believe that you have profit in altcoins only when you have profit in altcoin x BTc ratio.
2. Once I take the profits in stablecoins, is putting them on something like Blockfi to gain interest the best thing to do while I wait for another dip to possibly reinvest them?
I think it is too risk to put them in any lending plataform. You will gain 5-10% per year... that is very little in comparinson to 1000% gains bitcoin can still have in the next years, and you risk losing it all.
3. Once the bull run is over I'm most likely going to keep all my bitcoin and probably most of my Ethereum. I'll sell most of my alts for stablecoins but keep small bags of the ones I want to keep through the bear market. Is this a sound strategy?
Certainly. Bitcoin has better perfomance in long term compared to altcoins (in general, few random exceptions). I would consider keeping a hug amount of bitcoin now, at least 50%. Even in a bull market, as altcoins usually lose in AltcoinXBTC ratio in long term.
4. During the bear market is taking a cash loan using my crypto as collateral (BTC and ETH) a good way to defer capital gains taxes? Won't I have to pay these taxes eventually? I know there are drawbacks to this strategy but it seems like a lot of experienced people do this.
5. After the bull run should I just put my stablecoins in something like Blockfi during the bear market? Or is cashing out to dollars and investing in something like real estate a good way to defer capital gains taxes?
It depends on your country regulations and laws. In Brazil you don't need to pay taxes if you sell less than 5k USD per month. Additionally, if you are just holding in the bear market you don't have to pay any tax.
Dont worry about taxes in the bear market, just try to survive.