First impressions of Ridata BluRay DL discs

I recently got a chance to burn some DL discs and my overall impression was positive, with a caveat or two.
I noticed the read back speed accelerated until about 65 - 75% of the disc, then decelerated (read throughput) as
it completed the disc… Is this typical of a DUAL LAYER disc?
If so, then I’m ok with the quality… for what it is… Does burning at slower or faster speeds matter-- viable options to me are 4x or 6x… about 2 in 5 discs that I burned seemed to have faster overall read burning at 4x… so I can’t correlate that
success with the slower speed-- maybe just the laser getting it’s groove on after sitting dormant for so long…

It is normal that dual layer discs have a speed increase from the beginning to the end of the first layer (like single layer discs have), and the second layer is opposite track path, it goes from the outside back in, thus the read speed goes from high downwards (in the opposite direction).

Note that being able to read/verify the disc does not give you any idea about the acutal write quality though.