i got a assault tremy squad with a land raider transport (naturally) my question is "can i not embark my tremys (pre-game) into the land raider and instead just field empty transport and teleport my termys?" the rule book says the only limitation is i cant put another squad inside the land raider (pre-game) and the SM codex only says i can select the land raider not that i HAVE to put them inside the raider.

you can teleport the termys or put em in pre game. Also you don't have to take it as a dedicated transport. either way you can put other troops in it later

i know i can put other squads inside the land raider once the game starts but if i field it without the termys inside it and hold them in reserve so i can teleport them in; will the land raider count as a transport still?

yeah it is always a transport. you'll just have to load people into it in the first round since it can't be a dedicated transport for most squads.