Yes, the Honesuki was designed purpose specific to bone poultry, but damn does is it shine at boning thighs. Now, I'm aware your text says butterflying boned thighs; therefore leaving my comment moot, but I'm going to hope you mistyped.
That leaves us with the "two knife" conundrum you think you're potentially facing.
#1: There are those that use Hones as a petty; I have no phucking idea how. The angular axis of handle:spine:cutting edge is just strange (to me) as a petty & the tip is particularly thin & pointed, but humans are an adaptable species, for sure.
#2: I have never used/held the ArtiFEX, but it's description reads as a single bevel grind with an asymmetric edge grind. Sound like a kata-ha single bevel with a slight back bevel. Personally, I wouldn't want a single bevel petty for slicing garnish - depending on what it is, of course. Single bevels inherently steer... not my preference for garnish work. I don't see steering being an issue on sandwiches, but you'd be surprised on thick firm bread. It really depends on what you're cutting.
#3: You apparently are not boning birds, you're slicing flesh. Why would you want a boning knife (Honesuki)?
Get a 150mm petty with some height so you have a blade face to butterfly with, and a thoroughly functional utility knife that can excel at garnish work & cut your sandwiches. You have absolutely no need for a boning knife as you are not boning anything.
Your dilemma now is pricing; not much out there at a $70 price point. The Tetsuhiro
is probably the closest you can get @$100. It is not fully stainless, rather stainless-clad, but you're getting an awesome carbon edge in the trade. It's a little short for me, but still quite capable in your application. A full carbon Tanaka Sekiso
would be my number one reco, but I don't think you want full carbon. The Masakage Yuki
would be the best stainless-clad fit... if you're good with that, but it may be over budget as it is twice the cost of an ArtiFEX honesuki. And a fully stainless option, that just kicks ass but is $170... KaneG3