That's not the kind of joint I would do for that purpose. First of all, it's very difficult to find straight enough poplar to make such a joint line up after you cut the dovetails. I would more likely consider using some screws to attach the poplar strips, so you could replace it if it gets dinged too badly. I'd line up the top of the table with the poplar strips as best as I could, then plane the poplar flat to the table with a hand plane.
Or use a table saw jig like this to flatten the top edge of the poplar so it lines up with the table top.
I've been able to find a few, select pieces of poplar that were straight enough for face frames, but It's maybe one out of a dozen strips. I know our local HD restocks lumber on Tuesdays, so I go in on Wednesday early and pick the best pieces. I can find 6 and 8 footers that are pretty darn good in 1.5 inch width. You could also buy some straight wider pieces a bit more than twice as wide as the strip you need, and halve it with a table saw.
I personally don't really like the look of dovetails. Good for strength, but not very attractive to me. I think using them on a very long edge is just unnecessary overkill. IMHO.