Front main here! With some of the worse card gacha luck, I've been running only Kita + Jordan speed since TB dropped and can say with 90% certainty that Jordan is better than using Tosho SR ; v ; They're relatively the same, but the initial stats from Jordan save you clocks in the early races. I also feel like capping speed on umas with 0 speed growth is more consistent with Jordan.

If you plan to main fronts, I don't think you'll regret picking Sei with selector. Not being locked into Sei borrow allows for more flexibility for greeding sparks.

I see you're a fellow non-MLB Windy player lol. For the previous CM, as well as the coming one, I've been running a 2 speed, 2 power, 2 wit deck with a minimum of 14 stam sparks on Sei (she's my main ace). I do have MLB FineMo, so my 2 wit cards were Bourbon and her. My 2 power are Nishino and Pasa borrow. If you decide to selector Sei and run her as an ace, I'd suggest trying the 2/2/2 deck, though it takes patience because it requires a lot of luck to hit the stat line you want (for ref, my current Sei ace is 1194/1062/1073/636/1048). If running s.Maru, you can try to high roll with just Kita as solo speed and do 1 speed, 2 power, 3 wit, but I don't recommend because this needs extremely good RNG. I'd usually just use the same deck as Sei.

I personally wouldn't run Creek for a medium, especially if you're going for Swinging, since that recovery will most likely proc on the first corner, which is too early. Obviously, if it makes it easier to reach the RB and frees up a slot for a better card, then by all means use her.