A. Whether you decide on one subwoofer or three its imperative they be positioned within your rooms standing wave bass modes. This is a relatively simple way to locate and mark your rooms modes and is only done once.
https://www.audioholics.com/home-theater-connection/crawling-for-bass-subwoofer-placement
Using any other locations and you'll find yourself as dissatisfied as all those you read about griping, struggling or who've given up. DSP is not a panacea for out of position subwoofers.
B. Using a distributed subwoofer array or Swarm essentially eliminates the rooms modes and frees you from preforming the crawl. It also provides a unique and extremely encompassing low frequency presentation.
C. The last option is to use a -6dB sub-bass speaker (some also call themselves subwoofers). Regardless of how many are used or how large they are their frequency response begins a steep roll of in the mid 30Hz region. Since they simply do not excite the rooms standing waves they can be located most anywhere, at the expense of losing the true subtle musicality that a properly positioned and adjusted -3dB subwoofers provides.
Personal observations: More often than not speaker manufactures tend to design afterthought or needlessly over built premium priced subwoofers. They offer uselessly dated setup diagrams and/or complicated, or dealer adjustable third party signal processing.
High or speaker level connectivity was originally developed for customers whose receivers were without preamp outputs. If it were actually better everybody from Pro audio, sound reinforcement, and the majority of home subwoofer using it. Running the source signal through at least two more sets of inputs and outputs?
If the company provides you a list of speakers that their products are "matched" to, your in way over your head. Put simply, one adjustes subwoofers to any speakers not matching a particular speaker.
My current two subs have taken the place of four. It took this idiot less than an hour to crawl, position and run the Auto EQ which is 95% of the setup. The other 5% is making manual personal taste adjustments. The newer 12" sounds every bit as potent as the 18" it replaced. Unfortunately the company was sold in 2019 so I'm reluctant to make a recommendation.
Pull off your pants and jump in, you'll never go back.