Aroma is the gold standard, and there is little else to say.
I used Umbavapes unflavored WTA and I found it to be not as potent as Aroma, but for the price, decent and useful. I haven't vaped it straight, I usually purchase it in the nic strength that I want, and mix it in to my other (DIY juice) as we are talking perhaps 1/5 of a dropperful. That might be an option.
Ohm's vapes (which I believe is a sister site to Umbavapes) does offer WTA but only unflavored, and you can get 12, 24 or 36 mg strength (my understanding is the percentage of WTA is the same, only the nicotine level is changed. But, that could also be used similarly.
Aroma's WTA (DIY) is fantastic, has a slight nutty taste and aroma that is very nice. To be fair, I used Aroma in the throes of quitting, so it's hard to "compare" side by side, does the best with flavored WTA, in my opinion. It is truly excellent and very potent.
Mother's Milk looked (and tasted) like dirt. I made myself use it, but I did not order from there again.
Best of luck, I have found that using just a small amount of "pure' WTA mixed into regular juices (or even just into my tank) yields the best results (for me). Since I DIY that is the road I went down, but even trying to do that with Mother's milk WTA made things pretty unstomachable. The other two blended in nicely.... I got a hint of "nut" (maybe) with Aroma, and pretty much no taste with Umbavapes.
Best of luck,
Anna