Your CPU usage issue is probably just that old Ivy Bridge you are running at that very low clock speed. I'm running it in a Ubuntu VM with only 4 cores assigned (Ryzen 1600AF host) and my 15 minute load average is only 1.75. I've never used OpenALPR with a GPU but it is disappointing that you report that CPU usage isn't really affected much when using one.
I just emailed Rekor the other day and asked when the 4.1.1 was going to drop for platforms other than Docker since its been in the Docker hub for months now. They said "We don't know". And now here it is...