P300

I am bias and I still have a Winix for 10 years now, bought 2x wac5500. Ex-wife took one. Bought another type of Winix a few years ago. They are all still going strong. I have some 300-P coming in a few days, but they are intended as more supplemental units to help boost a higher ACH while maintain a lower noise. I liked the size of the units, and I bought them for $45 in like new condition on amazon. And filters are cheap enough. The size of the units I looked at and immediately thought they would fit nicely on shelves and other places so I wouldn't take up floor space with another larger unit.

I have the first leviot on your list, it works good for pet hair and js fairly quiet. I dislike the winix because it has the plasmawave ozone stuff that is on by default. The winix is very strong but it makes my lings hurt if I forget to turn it off

We have 3 of the winix plasmawave from amazon and they seem to work okay

Just make sure buy a modern model. HEPA filters have evolved a bit over the years and so has the regulation. Old "HEPA" filters might not be true HEPA by today's standards. Just make sure you don't buy one with an ozone generator, or if you do, since many come with it (my Winix with PlasmaWave, for example), remember to deactivate it. They are not very good for people's health and I guess they are far worse for birds For reference, I have a Winix Zero Pro

Air cleaners/purifiers (I have one in every single room, 2 in the open living dining kitchen area). Some brands offer pet specific filters (I use Winix plasma waves in larger rooms, and Levoit for smaller rooms, both the cylindrical and the rectangular). Regular vacuuming. Blankets on furniture that can be put in washing machines. If you have hardwood, minimize your area rugs and mop once a week, if possible. If you need area rugs, try washable rugs you can toss in the washing machine. I have three dogs, a breed that is notoriously difficult to house train. I keep an armada of enzyme cleaners and a black light on hand. They are also a breed that loves blankets, so I use specially formulated enzyme cleaner in the washing machine when I wash their blankets. The washing machine runs daily here.

Just throwing this out there to help with allergies. As you said you have lost your elder dog (rip buddy). Is this new pup the same breed? Just because he was immune to the other dog don’t mean that this one brings new allergies. But it can signify that it’s a different breed that kid can not tolerate. Each breed sheds differently from the other. Some more then the rest. Just a thought. I’m allergic to cats and dogs. But more so cats. We have the homedics 5-1 that really helps. But it’s recently gotten so loud that we are making the switch to the Winix brand. I would recommend staying away from the Lrg round units. Go with a rectangular one.