I've been running almost like for like in the playerroles as you and had decent success doing so, however, i have way more indepth TI's.
First of all, Douglas Costa is absolutely not what you're looking for in a Mezalla in this formation. You need someone with good workrate, decent tackling and even if it's not highlighted, positioning. In fact, you have pretty good options for that role in Ramsey, Bentancur and Can. Who of these will do the best job for you depends on your overall team instructions imo, but speaking from experience the Mez-s in this system plays mostly like a box to box. In fact, i frequently switch it with a BBM with the instruction of staying wider and there's hardly a difference in play between the two. I'd say the bbm is slightly more direct in his movements and aggressive in his pressing while the mez tends to combine and underlap with the wingback a bit more. But these differences are absolutely minimal.
With that being said, you probably want to put your left wingback on support duty as well. Your only width is going to be created from the wingbacks so you need them to be involved. Particulary because the Carrilero and the DLP-d already provide more than enough cover.
As for the attacking trio, a shadow striker can work fantastically and Dybala has (almost) the perfect PPM's for that. You'll ideally want him to have come deep, tries killer balls and plays one two's. However, the dwells on ball will likely be a problem as you don't want him to slow down the pace of your attack. In front of him you need players that he can play off of. Meaning you need someone to hold up the ball for him so he can start his runs and he needs someone that pushes up in front of him and/or drifts out wide so he can feed someone through balls and have the space vacated when he pushes in himself.
I personally think the hold up striker is key to this system and dictates how you can play it. I had lots of success with a target man on support in this role with a high pressing, high tempo system. Which is how e.g. Nagelsmann and Tedesco set up their teams in the Bundesliga. The idea being that your number 6, in this case the dlp, drops off and starts play together with 2 ballplaying defenders, or in Nagelsmanns case sometimes even the wingbacks, looking for either a long pass over the top for the faster striker to run into try to aim a long ball on the target man. Said target man then either let's the ball drop for someone to run into the ball (which your SS and to an extend the Mez/BBM and even Car are really good for) or he loses the ball, which imidiatly initiates a counterpress with the opponent being in an unexpected transition themselves, opening up space for a quick attack against an unorganized shape if you can win the ball back. The term for this is a "planned misspass". And you can replicate that actually fairly decently in the matchengine. In this scenario a AF-a or P-a would work great. Since you're likely playing Ronaldo, AF-a should be fine. What you definatly don't want to do is to play a Poacher with the SS, as the Poacher occupies the same space the SS wants to end his run at and doesn't create enough movement and space for the SS to play off of.
The other option is you have is to play to play a less dynamic, more controlled short passing game, in which case, pair the SS with a DLF-s and most likely a CF-a. Makes for a real fluid front line that can string together lots of beautiful passes.
Personally, I'd go with the targetman system, as it offers you three widely different ways of attacking:
- Long Ball bypassing the midfield from your BPD's or DLP (and at least for me my WB-s tend to do them as well) and then a 2 or 3 short passes with tons of movement from your front three to fashion out a chance
- The planned misspass, where you basicly use a missplaced long ball to spring a quick counter from a counterpress
- Cross from out wide after combining down the flank, mostly happens to the side you run the mezalla on. Or an angled early cross from the half space, which your Mez and Car will often times play.