This is my experience with TempDB. The Algorithm works better when the TempDB File sizes are the same size.
We were seeing heavy TempDB contention on a TempDB file that was larger than the others. We needed that file larger in the case of run away queries (caused by people not logging off their machines properly - not the SQL Server) which occasionally caused TempDB to fill.
We switched to 16 TempDB files (16 CPU's) on RamDisk all the same size with No Autogrowth.
We setup a job to kill the spid using the most TempDB resources, once TempDB was 80% full.
In working with Microsoft, their technician tested if a TempDB file was created on one TempDB file it would overflow to a second TermpDB file if it needed too (I was concerned about this).
Our SQL Server is a Read-Only AlwaysOn and we run some pretty big reports that use large amounts of TempDB. Our new TempDB design has been in production for over 6 months, with no issues. Occasionally, we have a spid cancelled due to TempDB over 80% full, but not very often.
Curious, is there some SQL code I can use to quickly determine if files are crossing multiple TempDB files? We are on SQL Server 2017 CU 12.