Depends on your design.
Short answer, bubbles will accumulate and reduce the efficiency of flow out of the tank.
Yes... that means your return pump might overrun the outflow if it gets bad enough.
A catastrophic failure of your vacuum pump could, in theory, break the siphon. So, it’s a remote risk both ways.
I never used an aqualifter - ever - over 6 years of running diy weir-type overflow boxes on my tanks.
It takes monthly maintenance, routine inspection (like every time you feed), but I found them to be relatively frustration free. YMMV.
Experience: many years and a few tanks running DIY acrylic weirs, both molded and u-tube styles. Used them on client tanks when I set up and maintained them for a living, on occasion.
Check out the diy acrylic weir design over at Melevs Reef. They work well.
I will never consider using one again. Drilling is too easy and makes life so much better.
Take that for what it’s worth.