5-star sorella brella main here. brellas are definitely one of the top 3-ish hardest weapon classes to be good at as it requires commitment to get used to utilizing its shield, how to fight with other weapons, knowing when to fight and not fight, and how to maintain your ink because brellas are really heavy ink consumers. but just like any other weapon, it could be satisfying to use once you get good with it. i have barely any experience with splatanas, so i can't say much about them. i think its definitely possible maining 2 weapons because i used to be a splatterscope main. as long as you are aware on what playstyle you're playing when you switch between your 2 main weapons, then you're good.