You need to be more specific about what you mean by "support" and also from which point of view. Does support mean things like personal preference and maybe free things like prayers and social media posting or actual tangible stuff like money and life? Also is the support from my own POV or Singapore's POV?
My personal preference is as follows:
Russia vs Ukraine = Support Ukrainians in terms of calling for peace and perhaps sharing a few donation appeals on social media. Condemn Russian aggression on social media also can.
China vs Taiwan = Neutral, don't really care, but if there is no war of course it's the best outcome.
My take on what Singapore should do:
Russia vs Ukraine = Don't kaypoh and mind our own business. If US keeps pressurizing us, then produce some perfunctory surface support, but never do anything substantial or irreversible.
China vs Taiwan = Support China in whatever way we can behind the scenes while pumping up rhetoric that is slightly slanted towards US but maintain general message for peace and prosperity.