A lot is going to vary depending on the exact game you play, strategies and game mechanics can be super different. The best way is to find a character that you really like and focus on having a good time. It’s a genre built off of learning from failure, so you’ve got to try your moves in different situations and see what works. You can practice moves against bots to find what situations they work well in, and plenty of people post combos you can learn online. Just gotta lose a lot.
It’s not “retro gaming” but that doesn’t make emulating switch games a bad thing. I dump and emulate my own switch games off my own switch because they tend to perform better via emulator on a PC. It’s really unfortunate to see Nintendo shut down what ultimately is the best way for us to preserve switch games long-term.