If a US very early-stage startup hires a Canadian and grants them restricted common stock (similar to what founders get), what are the implications for them (1)

If a US very early-stage startup hires a Canadian and grants them restricted common stock (similar to what founders get), what are the implications for them (1) from a Canadian tax perspective* and (2) if they move to the US later on*? *(1) e.g. is there anything like the 83(b) election or similar. *(2) how do 83(b)s work for folks that might move to the US later, especially given "might" ?