Alright, I would wish you to elaborate on the assumptions for fantastical elements.
I suppose classic humanoid races are fine. You did comment me on that there won't be any explicit magic, though.
Also what about typical fantasy materials like mithril or using alchemy-like methods to produce chemicals that have capabilities beyond what we would have in reality?
I would think if fantasy races are allowed then so are such elements but I'm certainly not the GM here.

Also saying it's 1910-1930 tech is actually fairly vague.
Dates in general are pretty vague because we could've skipped many decades in development if certain people thought about these inventions sooner.
Add the fantastical element which may negate the need to wait for more proper materials (because they already exist) or sufficient industry (because you can have them sooner) thus you may as well run around with early cold war era weapons in 1914.
So yeah, I think this part is subject to change.