Alright, so I did some basic testing. Seems mutable or not makes only a tiny difference in my case (within repeatability). However, defining one of my vectors as
Vector{StaticArrays.SVector{3,Int}}
vs
Vector{Union{ StaticArrays.SVector{3,Int},StaticArrays.SVector{4,Int} }}
or
Array{SArray{S,Int64,1,L} where L where S<:Tuple,1}
makes quite the difference (20-30% for the first, 2x for the second). The discussion on these definitions is here Struct variables explicit setting so I got some tips already.
So other than my crappy way of defining my variables, structs seem ok (and the same as passing vectors). I’ll still have to figure out how I can have a Vector with SArrays that can be 3 or 4 elements long.
Thanks, everyone.