- Can I start my wallet now, or don´t touch it till update ? (I only want to open it, no tx´s)
Yes. There is absolutely zero risk with using Bitcoin as of now. It is not called update, its just a fork. The only risk I can see as of the fork is that the replay attack can occur which Bitcoin Cash has protection against.
- Will the core devs (bitcoin core) support the chain with segwit, they were against it weren´t they ? (not sure about this), so what wallet to use after update for the original chain ?
They were for segwit, not against. You can honestly just use any version above 0.13.1 if you want to use segwit. Most version above 0.12.0 should be fine, if you do not wish to use segwit.