>>50863814Pikalytics, Smogon and Victory Road are places I would suggest looking at. Both formats are good (unless you're playing singles with dynamax) but there are some mons/moves that are better suited for one or the other. Like entry hazards are mostly useless in doubles but are almost necessary in singles while you don't really run protect in singles despite it being very popular in doubles.
I'd suggest watching a few streamers/youtubers that actually explain the thought process behind their moves and the mons they bring for that matchup. Cybertron is a guy that mostly just explains the game as it goes by and doesn't have some overboard persona to generate more views. Wolfy is very autistic and understands the game well while explaining what he's doing but he's kindof an annoying faggot.
If you're interested in singles I'd probably say Showdown/Smogon is definitely the way to go because I enjoy 6v6 more than 3v3 that you do in BSS on cart. If you look up a Pokemon like Bisharp for example there will be a few sets for it with explanations as to why each move/ability/nature/evs/ivs are chosen and then give you mons that have good synergy with Bisharp and also counters to it.
>I haven't even thought about team composition and stuff like that but I saw that one video where Jadenanimations makes a competitive team with Groudon and Charizard, I was wondering if that's actually viable outside of random online Switch battles.For doubles it works, Venusaur is also a common mon to add to those two.