My dentist advised electric is gentler but much more thorough. So I changed but I still use a regular brush at times. Manic brushing up and down tends to damage gums and reduce them, and you miss bits. Electric goes ‘round and round’ at many 100s rotations / minute. It’s a lot easier on the hands (you don’t apply pressure). Just make sure you cover all surfaces. In front, behind and on top. ie do it ‘mindfully’. You still need to floss (or water pick if you like that idea and can afford). Or use interdental brushes. Rinse well. What suits you will depend on your own teeth and their issues, gaps etc. Get in the habit of rinsing with water after any eating where you don’t brush. If you use an electric toothbrush - as for a regular one - keep it clean and change the head eg 4-6 weekly.
Diabetics may suffer more mouth/ gum problems. I have them from a much earlier condition. Meds (dry mouth) and poor brushing technique. Whatever the cause - gum disease is now associated with dementia and other poor outcomes. The reasoning goes along same lines as poor ‘gut health’ - when weak endothelial cells in your gut don’t contain all the nasties in your bowel and some leak to blood stream. This can cause inflammation of various types (among other things). Inflammation is ‘bad’. So gum inflammation is bad. There are degrees though. So don’t panic. You can have damaged gums surgically repaired. I haven’t yet - as not quite beyond help (it’s not fun). I am in Oz where dental services are more available (compared to uk). We know brushing 2x day, 2 mins is recommended. I take longer.
I imagine a Lowcarb diet helps to reduce excess plaque. (Starch digestion starts in the mouth). So that’s another win for LC. Also if you are in throes of diagnosis (eg with peeing a lot and drinking a lot), saliva production may not be optimal either. Besides brushing technique you need to consider if /why you have a dry mouth, and address that. It may be as simple as - drinking more water (and not other bad drinks); a change of meds; or a spray to help moisture stay in your mouth.