I don't do builds without adjustable gas blocks anymore. They make everything so much easier and the rifle runs optimally. The only two adjustable gas blocks I would reccomend are the Superlative Arms (to set once and forget) and the Rifle Speed (on the fly adjustment for suppressed), depending on which way you want to go. I don't use the blow offsetting on the SA anymore because it can be a bit finicky to tune and you lose a few fps by venting vs. restricting.
There ARE lower limits on the quality of low pro gas blocks. I used a Sadlak (sp?) fixed gas block once that was under $20 to see how cheap I could go at one point and it was a freaking nightmare. The journal was too small at one end and had to be hammered on the last 1/8" and even using a small brass hammer, the steel was so soft it peened under a few strikes with a brass hammer. It had a gas tube roll pin hole too big for the inluded roll pin and it would not work. The finish was the worst bluing imaginable instead of parkerized or other quality finish.
For a fixed gas block of 0.750" I found BCM to be the best value. I don't like their 0.625" gas blocks because they use the same steel profile as the 0.750" gas block and just cut a smaller hole for the barrel. This makes the 0.625" gas block heavier, not lighter, like a propperly proportioned gas block. And if you are doing a 0.625" build, you probably care about weight. Also, BCM has a more gray finish than black but noone will see you gas block under the rail... but for some OCD people it's a thing. Otherwise, great kit at a great price.
I also prefer set screws with a circle ring of teeth to cut into the barrel and not require a dimple to be secure vs the pure tapered point style.
You only need a single dimple opposite the gas port if you have a barrel dimple. If your barrel has more than one dimple, be aware that set screw spacing for the set screws is a thing and you can end up with a set screw on the edge of a front dimple rim if you choose wrong. Not having a second dimple on a barrel is best IMO.
I don't reccomend a clamp style gas block because they often don't fit well under slim rails. There are some myths that a set screw gas block can harm accuracy vs a clamp style. I have found that to be utterly false, even on pencil barrels.
But no, you don't need a Badger Ordinance SPR gas block to build an upper. Just don't go uber cheap.
What are the differences in low profile gas blocks as money goes up? There are differences in the hole that covers your gas port to make fit less critical, but a single dimple opposite the gas port makes that a non issue. The steel itself can be substandard only in ultra cheap blocks. The 0.750" hole can be under or oversized only in ultra cheap gas blocks. The finsh can be different. The set screws and spacing can be different. The gas tube roll pin hole can be nicely chamfered at the very end or not to make gas tube install easy or a pain and that hole can vary in size. The gas tube pin can be included or not and it's quality and size can vary quite a bit. I usually just use the one that comes with a particular gas tube. You also want to stay away from gas blocks that don't appear to be of the SPR profile shape as they can have fit issues under slim rails.
And if this is your first build... remember to install the gas tube BEFORE you install the gas block if the barrel is already installed or install the gas tube AFTER installing the gas block if the barrel is off the upper and you don't have an SPR gas block install jig. It's a pain to keep the block still and get that roll pin started. Finally, be sure you don't install your gas tube upside down and have to do your gas tube install a second time.