Personally I don't find either of those choices necessary. Tag arena is basically the only arena place that requires any real development of your champs, and it just requires what Trips is explaining.
Focus on building and developing 3 teams that can win, and learn the types of defensive teams that each of your now strong teams can win against. As he explained in another thread, if your teams are too slow for your taste, then you've still got room to keep iterating and building. If you can't win a high enough percentage of your fights, there's still room for gear farming and team design. If you're losing a TON of defense fights through the weekend and on Sunday, when people put their real teams in, there's a huge space to improve your defenses with gear, tuning and team design until you start seeing wins in your defense log, or aren't hit at all.
And you can get help developing your teams and strats here and in your cluster discords and from your clannies. I know I asked for a lot of feedback and help when I was first pushing into Gold Tag forever ago, before even the first player cap increase. The size of the cap hasn't changed much for me, I still hover in G4 Tag regardless, but the advice of other players made a huge difference. And yes, at first that advice was partially "Get farming, you need to drop 30k Fire Knight runs to get started" but it also included team suggestions and importantly, what kind of teams each suggestion was meant to face. It definitely took a decent amount of farming, playing the mode, and working on my teams.... but that's the game, leaning the fights and building teams to win at the rate and speed you desire, that's what the game is.
Basically though, all the other arenas are participation modes. Players fight one champ teams in Classic and have a 20 loss cap on defense so they can feel like they're great and sit in Gold 5, regardless of if they're doing it with a solo login champ in starter login gear. Live Arena lets you get to Gold with what, a 30% win rate, as long as you just queue every day? 3-7 and 2-8 mostly fine as long as you're just playing the mode. You can even place Plat just sneaking in by refreshing to find a trash page then hitting all 10 of them right at reset.
I don't want Tag to also be participation medal only. So much of the game devolves into just 1) click button 2) wait 30-90 seconds 3) win that I don't feel asking people to build 12 strong champs in a set of three teams is too big an ask for a single game mode. Just my thoughts though.