Hiya there. I’m not a SS expert, but I’d like to state my opinion on this.
1) If you overlevel your Pokemon enough, they should be able to outspeed anyway. Of course this is a harder point to justify with such low base speed.
2) I don’t know what point in the game you’re in but I did some calculations with a level 50 Azumarill (with showdown ofc) since that’ll be a good level later in the game. A Jolly level 50 Azumarill should have a speed stat of 115 if I did this right (assuming there are 0 EVs in the stat). It’s not terrible, but not amazing either.
3) This seems like the only time I would recommend using a Choice Scarf ingame, purely because you want a fast Pokemon and Azumarill falls short of that.
Basically, do what you’d like, but this is what O think about it.