I do the backdoor Roth every year. It's very simple. I'm not sure how it works through anyone other than Fidelity, but I use that since I had an old traditional IRA account there to use as my conversion vehicle. Here's the basic steps I take.
First, you have to make sure you don't have a balance in ANY traditional IRA account. If you do, you can still do the conversion but you'll be taxed on it (pro rata). 401K accounts are exempt from this. So, you move all of your traditional IRA funds in to your company 401K. Once you've established a zero balance in your traditional IRA accounts (all of them), you're ready for the Roth conversion.
I make a non-deductible contribution (via a savings account) to my traditional IRA of the full maximum amount of $5,500. Then, within Fidelity, there is a menu option in my traditional IRA account to "Convert to Roth IRA". I convert the full amount over to my Roth. That's it.
As for whether you should do one or the other ... IMO, and I'm not an expert but, I would think from a purely financial perspective, the Roth contribution is preferred if you can't do that and put a down payment down. You get tax free growth and it should grow at a faster rate than a property. Since the Roth is capped at $5,500/year anyway, it sounds like you can do both, it'll just take you a little longer to pull the trigger on the house.
Another thing to consider is that interest rates are historically ridiculously low right now. If your goal is to get a low monthly payment, I think the safe assumption is that rates are going to go up from here. If it does, you may be borrowing less (good), but paying a higher interest rate and so net-net, your monthly payment could be the same. I'm sure there are experts here who would know best, but, have you thought about pulling the trigger on the house, and then, if interest rates stay low, refinancing later? So you'd buy the house, keep saving your "down payment" and Roth, and then if you've built up a nice chunk later, you can refinance and put that down to get your payment down.