We don't have any info on Alina yet but here's what we know about Touka and Nemu, MTL'd so it might not be completely accurate.
Touka is a ST fire breaker who synergises with follow-up attacks, making her gain a stackable SPD buff. She also gets a follow-up attack when a special is used and she has 2 or more buffs which increases her turn order by 20%.
She seems like a better ST breaker option than Iroha and Rena in cases where the boss is weak to fire OR in cases where the boss is weak to void/dark and not water/light as she benefits from being paired with Ren or Homura.
Her ascensions are surprisingly not that interesting, with A1 being the most interesting one increasing her break gauge reduction and also increasing her speed by 20% for 2 turns after breaking an enemy. Her A2 seems to be made to allow her to stack her speed buffs better without the help of Ren or Homura while A4 is the generic breaker A4.
I think however that the most interesting part of her kit is her support ability. She can support breakers, increasing break gauge reduction and also increasing speed by 25% when at 2 buffs or more. This seems like the best support for Pluvia Madoka and will be particularly strong in PvP.
She's alright, our first 5* fire breaker who, unlike Karin, is speed based, but I don't think she's worth going for despite the 5% SSR rate. It'd be best to be patient since she's getting added to the general pool at the end of july, alongside the Amane twins, Mabayu and the other Magius.
Speaking of other magius, the other 5* on the banner is Nemu and she's a poison-based forest debuffer.
Her entire gimmick is to apply poison with her follow-up attack on specials, which also applies a 10% damage taken debuff. She applies more poison (doesn't stack) and lowers defense by 20% with her battle skill. She can also increase forest damage by 30% and consume her poison (just like Hanna) with her proximity special.
Overall, the poison damage is only really there to fulfill some ailment or poison condition on a boss mechanic. I don't think the damage is gonna do much. The 30% debuffs + 30% forest damage debuff however are interesting, especially if Holy Mami ends up being a forest attacker. The follow-up attacks make her synergise with Touka but I'm not sure why you'd go with her instead of Ren.
However the most important part of her kit comes from her A2 giving +30% damage dealt to poisoned enemies. This buff is of the same type as her follow-up attack debuff but it's multipicative with her 2 other debuffs, which should increase damage quite a bit.
I think she'll definetly get to shine and might be worth going for if you're aiming for A2 and if the next stream takes place before the banner ends and a forest attacker is announced for july (or if Alina ends up being one). Otherwise, better be patient again.