Quality of various NMN products

So following the work of Dr David Sinclair ....about 5 months ago I added NMN to my daily supplement regime, taking 500mg on an empty stomach every morning about 7am.

So far I can't claim to notice any differences in how I feel which has got me wondering about the quality of the one I've purchased.

The one I have is Nutopia 500mg (60 capsules) https://nutopiausa.com/products/nmn-500mg-%CE%B2-nicotinamide-mononucleotide

I notice that the bottle says "Beta" Nicotinamide Mononucleotide and I'm wondering how the addition of the word Beta in the formulation affects anything good or bad and if maybe that Beta has to do with the FDA wanting to stop sales of "straight" NMN???

The next thing I've noticed is that like pretty much any supplement you can buy that prices are all over the place from relatively inexpensive like my $25 dollar bottle of NMN to over $100 bucks for some .

Does it really need to cost more then $100 per bottle to work???

This next makes me think that I should consider getting a blood test for NAD levels and possibly adjust my dose accordingly based on that.

Here again prices for NAD testing are all over the place! From as low as $100 for an at home test that you send in to over $500!  Does it really need to coast $500 or more??? 

So does anyone know of a lab for reasonably priced NAD testing that they trust to test correctly????

It'd be great if LabCorp offered it because if they did, my doctor could prescribe it and insurance would pay for it....but oh well to that....they don't!