This is something I have struggled with for a long time. I finally did a search that came up with this link.

Different low carb doctors have different ideas. Bernstein thinks diabetics should have and target the same blood sugar levels as non-diabetics (he personally is a type I insulin dependent diabetic and I highly recommend his videos for any type I diabetic and he also treats type II). Other doctors seem to be ok with higher levels. This may give some guidance for those who also have faced the question of "how low should I try to maintain".

https://www.bloodsugar101.com/organ-damage-and-blood-sugar-level

Edit: Summary. What I took from it is if a pre-diabetic or diabetic maintains fairly level blood glucose anything under 140 is not too bad. If a person is having spikes considerably above this level (like most diabetics eating a standard diet) then the fasting glucose should be dropping down to around 100. Needing this lower fasting glucose does not seem to be as important if the levels are maintained fairly uniform throughout the day without the big spikes. That is what I took from it. If anyone reads it differently please discuss. I don't think it is the end all of the discussion, but at least he lists some research to support his ideas. I have heard from several sources that the spikes in the glucose are the most damaging rather than the overall glucose level, but I'm not sure that makes complete sense to me.