HPA5200B

They're not the quietest* of all available options nor the cheapest but every one of my Honeywell devices has worked very well with daily use for 5+ years. I bought them on sale, watch for filter sales online (I buy the Honeywell brand as I haven't found good testing data for knock offs) and I have no regrets. Models I use: Honeywell Insight in Medium-Large (x2) and Large-Extra Large (x1). * They do run quietly on lower settings but I generally use the higher two settings.

Mine is a Honeywell. Because I know I'll be able to continue to get filters (even if I do buy off brand ones, bc theirs are SO expensive). Standard filters is the way. The A+ prefilter is better than the standard softer A style, but both are good at catching cat hair (I vacuum it off regularly)

Honeywell makes standard styles/sizes (mine uses two R filters) and other companies use the same system so it's easy. You can also search by model number (ex hpa 200) These are what I bought last time: https://ebay.io/m/JRqZjg

Yes. I have Honeywell HEPA units in multiple houses. 24/7.

For reasonable VOC removal there are only 4 players I know in the market which offer products which have the minimum 10 pounds of sorbent media: Airpura, Allerair, Austin, IQAir. Wildfires product a huge mix of chemicals - from the vegetation, contents of burned buildings, etc. There is no consumer solution that removes all VOCs. Each type of media is better at some chemicals, not so good or not effective at all with others. For the same reason there is no sensor that I know that will give you the level of all VOCs. These machines and filters tend to be expensive. I just upgraded my Austin units with Immunity Machine filters which cost \~$700 each. We were spared wildfire smoke this season but with AQI numbers breaking 100 I was able to keep my indoor values close to 0. I use Austin and IQAir VOC machines along with Honeywell and Whirlpool HEPA units, 3 filters per room.

My old Honeywell HEPA was maxing at that, but any certified HEPA filter would work. Just make sure you get the proper size and/or put them in different rooms. We currently have 4 (3 room only, I larger Blueair) due to allergies.