the only effect it can have is to delay it slightly by making more talking points between completion of the romance
for torian and mako to be romantic you need to actually keep choosing that option and encouraging it. if mako is on that story arc you will not be able to romance either of them until you either tell them to stop talking about it (as in take an option like, its not gonna work out) or you let it go to the end of its storyline (which isnt very deep) and they end up breaking up anyway and than you can get back to romancing either one of them depending on your gender/affection
the only thing the mako/torian romance does is create a series of extra conversations which lead to you either telling them to break up or you encourage them and they fail on their own and break up and than its back on track with whatever other companion arc you were on
thier romance doesnt happen at all if you already are on a romance arc with mako prior to getting torian, but its at most slightly delayed if you do it the other way around
as a female bounty hunter i had to jump through the mako/torian arc before being able to romance torian myself, it took all of an extra 10 minutes of conversations, so its not even a big delay. and yes i was actually encouraging her to go for him so i could see how that would play out, because i didnt care about romancing him myself, but the option to do that came up later anyway since they fail.
If I could give you a batch of freshly made cookies from the oven through the internet, I so would do that right now.