No steak expert here, either, but ligrill even with thin steaks, a 4 min sear "and that's it" (if I understand you correctly) sounds rare-ish, med rare if that's your goal?
If you cook more than one at a time ... you can experiment and arrive at a desired result by offsetting the coals to one side, creating direct and indirect areas. Cook one as you say, quick sear and another indirect for longer and see what you like better. In either case I'd be in the habit---nearly always---with leaving the lid ON.
As for the taters, I'm not a fan of putting aluminum to food but I'm sure there are stainless steel potato nails. Weber sells some that are probably like that? On the other hand, for other, longer cooks where you're doing meats/veggies here and there for like an hour, just put the potatoes right on the grill and let them cook for that hour, turning, moving closer/farther.
I like them "near" the coals. Too far away is too far, right over the coals turns the skin black if not watched ... and being able to leave the lid on while meats get their magic is part of Weber's magic, you dig? So midway between a direct and indirect cook for potatoes that'll be left on for about an hour while the rest is happening.
That said, potatoes down in the basement (i.e. with coals, on charcoal grate) works fine, too, and gives you room up top for veggies. They tend to be fairly forgiving. Remember, heat rises, so down with the coals isn't necessarily hotter. And if you wrap them in foil, that retains heat if you need a faster cook. Lots of options! I prefer simple, no foil, and that does nice things to the skin for flavor.