My take on it though I am not professional, and brewing for about 1 year (not counting experience with Pinter):
Fermenters: Plastic vs. glass—what do you prefer? - I prefer plastic: 1. It is cheaper, 2. I like watching how it brews, 3. The signal from Rapt Pill is reliable; 4. I brew under pressure which is good for lagers and IPAs
Brewing Kettles: Best size and features for beginners? - don't use it, I buy kits and because it is faster and more convenient. Also, this might be the cheapest option
Airlocks and Stoppers: Best types and brands? - don't know, I got two somehow and I do not see any difference
Thermometers and Hydrometers: Recommendations for accuracy? - I use Rapt Pill for convenience, it tells me alcohol %, temperature, duration, and very convenient
Cleaning and Sanitizing: Top products to use? - ChemSan, ChemClean? I save the sanction water and reuse it, so far no problems after circa half a year. I do not always clean the keg either if I put the same brew from the same manufacturer
Measuring Tools: What’s essential for precision? - Rapt Pill, it is not that accurate as it measures gravity +- 0.002. However, it is good enough for me, I wanted accuracy at the start, but now I am not that bothered as long as I know when to stop fermenting
Bottling Supplies: Key items for a smooth process? - I have two kegs 19 litres, people advised me here to get them to make life easier and they do. I have 2-litre plastic bottles (Cola, Fanta etc) and other 0.5-0.7 plastic and glass bottles too. Usually I drink from keg and give away 0.5-2 litre bottles. Then bottle capper (I think I spent about £10 on eBay for new one, it looks like this and you won't risk breaking the bottle as happens with cheaper ones
https://brew2bottle.co.uk/products/...l0auREqExlTmhFVD_aeHTWYZtDxLbclcaAlM4EALw_wcB ) and caps. And I now started using carbonation drops instead of priming sugar - it costs more, but sugar causes rapid foaming and starts spilling if you do not bottle it fast, so less messy and easy to use
I also got myself fridge and Keg Washer/Fermenter cleaner. This keg washer looks a bit better than mine and cheaper, it saves a lot of hassle cleaning
https://www.themaltmiller.co.uk/product/keg-king-cleaning-kit-corny-keg-washer-and-fermenter-cleaning-kit/?v=79cba1185463#:~:text=The Keg Washer from Keg King is an affordable, efficient,sediment and residue with ease.