Well, the game's focus is female muscle growth. As such it makes up 99% of the fetish themes. For the rest you can expect stuff like breast growth, mini giantess, demonification, futa growth. Everyting will depend on the character's physique and personality for what grows - some will grow taller while others will experience breast growth. Most growth themes will be present though.
Are you interested in a particular fetish being present? If so I can tell you if it is possible to come.
Will several fetishes be represented in one character at once? I mean, will it be possible to see gts/mini-gts, breasts expansion, fmg in one character at the same time, or will it be one character - one type of growth?
Also, would you plan to add a hyper?
Will you plan adding fat growth (I don't know, how it call) because in games which contain growth, is quite common (i am personally don't have interest, but i saw comment about preg and remembered about fat Growth/gain)
Every character will for sure experience muscle growth. No way around that. What other things grow will vary from character to character so it is not constrained to just one fetish. As there will be tons of characters to come you will probably get to see tons incorporated.
Hyper is not on my radar, as I personally am not a fan of it but there might be in the future nevertheless.
Weight gain / fat gain is a for sure a no. I hate this fetish so I won't ever do it. There will be some characters that are fat but not anything too extreme.