Seriously doubtful you'll get 4x sticks to work on a 1st gen Ryzen at anything over 2667MHz, and much depends on whether the ram is single or dual rank, (not to be confused with single or dual channel) or what combination of ranked ram is used in which DIMM slots.
For instance; using SR-DR-SR-DR can get you 2667MHz, but using DR-SR-DR-SR will only allow for 2133-2400MHz. Ryzen are extremely picky about ram configurations as the cpu uses ram speeds to dictate the speeds it uses for communicating between its cores.
Single rank is one set of ram chips in serial config, so in an 8GB stick the info has access to the full 8Gb when it goes through. Dual rank is more like SLI, it's actual split into 2x4Gb on the stick (parallel) (usually has ram chips on both sides) so the info going in is split, some goes left some goes right, flip-flop, so only has access to 4Gb at a time. Sometimes dual rank is a bonus, sometimes not. With Ryzen, it's generally not as the infinity fabric can get fuzzy when dealing with so many flip-flops with 4x sticks, leaving SR as a superior choice. Ryzen also use A2/B2 as primary channel, that's its first choice and gets better performance. A1/B1 is a secondary channel and pretty much only sees use when the primary is swamped.
You'll have to use a program like Typhoon Burner to see what the ram is, single or dual rank.
If old set is dual, new set is single then placing ram would be new-old-new-old will get 2667MHz. Placing old-new-old-new will get 2133MHz.
If old is SR and new is DR, then opposite applies. If both are SR, or DR, then can place in any order and get 2667MHz.
Timing changes/voltage changes will have very little (if any) affect.
Ryzen simply do not like 4x sticks. 2x in A2/B2 is best performance and only way to attempt greater than 2667MHz.