Using a SDG2042 at 1KHz (Edit:10KHz), {100KHz} Sine, [10KHz Triangle], 1Vrms setting, we just did a quick sanity check with these, all in Vrms (SD):
SDS2000X+ in 10 bit mode 1.007 (1.007) {1.009) [1.004]
DHO814 1.004 (1.009) {1.005} [1.007]
SDM3065X 3Hz filter and average 0.999047 (0.999591) {1.002099} [0.999194]
KS34465 #1 3Hz filter and average 0.9999419 (1.0005105) {1.0008633} [1.0001987]
KS34465 #2 0.9999388 (1.0005261) {1.0005467} [1.0001601]
DMM6500 3Hz filter and average 0.9999689 (1.000422) {0.9996228} [1.000037]
AG34401A 3Hz filter 1.00001 (1.00057) {0.998214} [1.000133]
These DSOs are somewhat respectable for lower frequency AC RMS measurements, agree well with various DMMs, and of course should well outperform any DMM at higher frequencies.
The two KS and the DMM6500 utilize digital sampling techniques, while the SDM3065A and AG34401A utilize old school analog (AD636 maybe) techniques.
Would be an interesting involved test to see how well these old school techniques behave relative to the newer sampling techniques wrt to rms readings at various frequencies, amplitudes and crest factors.
Best,