For the makevars file, you need to have it in your Documents folder, in a folder named ‘.R’
So you need to create a folder:
C:/Users/dalto/Documents/.R/
And then inside that folder create a file called Makevars.win which contains:
CXX14FLAGS += -O3 -mmmx -msse -msse2 -msse3 -mssse3 -msse4.1 -msse4.2
The cat(...) command was just to automatically create that file and it’s contents (not sure why it didn’t work), you don’t want to have the actual cat(...) command in there.
As for the models, those warnings are all safe to ignore (the g++ one will be fixed in the next release). Do the models all compile and sample without issue?