Is Trading 212 safe?

I am about to about a stocks isa with either 212 or freetrade. I have been told that 212 are free and in general their conversion stocks are much lower. I plan on buying many USD stocks and I am from the UK. Would 212 save me a lot of money?

I don't mind the extra £50/year for the freetrade sub but if there fees are in general high then I am not sure