What is the best type of bed alarm to prevent fall and wandering?

Cgore76: Perhaps it's time for managed care placement. Falls cannot be prevented.

A bed alarm will NOT prevent a fall nor will it prevent wandering.
NOTHING will prevent a fall. (OK, maybe if the person is confined to a bed or wheelchair...oops nope they fall from those as well.)
You can use a baby monitor.
that will alert you if he gets up. But it will not prevent a fall.
A tracker he can wear as a watch will allow you to locate him but it will not prevent him from wandering.
It may be time to get him in another room.
It might be time to get him a Hospital bed.
Lowering the bed so it is very close to the floor so it is difficult to get out of but also if there is a fall it will not be from a great height.

You can’t prevent falls. He will fall.

As for an alarm, my great concern is your lack of fully uninterrupted sleep and the heath risks that come from that. 30% of caregivers die before the peopel they are giving care to.

I would try the bed rails on his side of the bed. Maybe with the bed alarm?
I am so sorry, I know it is heartbreaking.

It won't be a guaranteed solution. My 100-yr old Aunt with advanced dementia shimmied past the bed barriers, took a few steps and broke her hip in her own bedroom. I'm regretting not putting her mattress on the floor.

I think a floor mat alarm might be the best option for you, or perhaps a motion sensor placed by the door. Baby monitors are also readily available and come with video options, you can turn off the audio for privacy.

https://www.agingcare.com/search?term=bed+alarms