Assuming you are just doing 5%, the most segment efficient path is to do V20 (supercharged amp) > V20 (any) > V20 (any), then repeat in an infinite cycle, which gets you 5649 RP for NM 1 for 10500 Segments.
Using amps on NM 2 and 3 as well is slightly less efficient in terms of total RP:Segments (0.538 RP per segment for just the supercharged amp, 0.525 RP per segment for amping all 3), but takes significantly less total time spent, giving about 25.5% more RP per 3 NM run. This can either be done all on the same NM by doing 5%, exiting and re-entering, and repeating, or the other 2 NMs can be other ones that you still need RP for, like Bumba.
The first pattern takes about 233.7k segments for 5 R25 pieces worth of RP, while the second route takes about 239.4k segments for 5 R25 pieces worth of RP. Getting 5 pieces to R20 takes slightly more tham half of those values.
If you're unable to solo 5% on your NM of choice, you can do them at a lower V level for an efficiency hit while keeping the other 2 NMs at V20. I've done some solo Ongo RPing on DRK at V11 (leading to a supercharge amp at V17 potency due to averaging V11 and 2 V20s), which is about 60% as segment efficient.