I've looked over your floor plan and reread your earlier posts. I think you are doing a great job with the proposed design. Venting out into the garage is going to be a must.
For those visitors who are left scratching their heads after reading badskater's first post, an "Infinity CloudLine T4" is a ducted fan and marketed towards indoor grow tents and hydroponics. I use a similar fan to circulate the air in my 3D-printer cabinet through ULPA + carbon filters.
Here are the thoughts going through my head, and in no particular order:
1. Server Room Temperature
I don't have any recommendations on your AC setup, just observations.
Why do data centers keep their server rooms cold? To reduce component failure due to heat. To increase time before a catastrophic failure due to high ambient temperature if the AC unit dies. But also note that server rooms tend to be large volumes of air. A large volume of air also extends the time before a failure due to high temps. Why is this important? Because those servers run someones business and absolutely must be online 24x365.
It's been my experience that home lab servers don't need to be kept at 65 F. 75 F or even 80 F is fine, reducing your need for an AC unit. But it is still absolutely a necessity during the hot times of the year. When it is hot outside, an AC unit has to work even harder to dump the heat. This is when AC design efficiency is most important. What lowers your AC efficiency is that it is a single hose design. It vents the hot air coming off the condenser to the outside (good), but the air to cool the condenser is drawn from the server room itself. This adds to the load on the AC unit because the air in the server room is replaced with hot air from outside the server room, which would be the Rec room or outside the house through cracks in the walls/floor/ceiling. A two-hose AC unit is slightly more efficient at cooling a closed room because a two-hose AC unit doesn't turn the room it is cooling into a negative pressure zone.
However, almost all of this one-hose/two-hose debate becomes a moot point because you are designing this server room to dump the hot-aisle air out to the garage, forcing you to constantly "import" fresh air into your server room.
The amount of heat produced by the racks will dictate how fast your exhaust-to-garage fans run. If the fans run too slow, the air behind the blankets will seep out from behind the blankets back into the cool aisle, forcing the AC to work harder to keep the cool aisle cool. If it runs too fast, the exhaust-to-garage fans will pull air past the blankets without going through a server. This will draw warm air into the server room faster than it needs to be, which will force the AC unit to work harder than it needs to be. It looks like your ducted fan has a temperature probe that can be used to control the speed of the fan. You will need to have that probe inside the hot-aisle.
If I were you, I would plan to increase the number of exhaust fans to cover emergency situations. Similar to how servers are over-built. They have an abundance of fan capacity and ramp up fan speeds when a single fan dies, giving you time to perform a repair. Also, consider what it would take to put those exhaust fans on the UPS.
Also note that if your main source of air into the server room is your Rec room, then you need to begin thinking about your home's permanent AC unit as part of the server room equation.
2. Air Filtration
If your server room was a closed/sealed room, then you could get away with an air filter that is fairly small. Once the air filter cleans the particles out of a closed room, then there isn't a reason to leave the air filter running full blast. But your server room is designed to have a constant flow of air through it. You are going to need a ducted HEPA air filter and keep the server room door closed, or your servers will be full of dust, hair, and that weird black crud that accumulates on fan blades.
The air filter, like the exhaust fans, should also be kept on a UPS.
3. Size. aka "Atsa lotta BTUs"
Your list of equipment is rather lengthy, and in my humble opinion, oversized for the room it inhabits. In fact, the list of equipment is so lengthy, I am curious if you priced renting space at a nearby co-lo and experienced sticker-shock.
If the power goes out and the exhaust fans are not on UPS, then the tiny server room overheats quickly, causing a failure. If the power goes out and the ducted air filter intake isn't on UPS, then the tiny server room is starved for clean air and overheats quickly, causing a failure. If the power goes out during the summer and the AC isn't on UPS, same quick overheating failure.
But perhaps this isn't a big issue. Perhaps all your servers are set to auto shutdown if the power goes out, meaning all you need are 5 minutes of UPS runtime. If you need more runtime, then you are now looking at auto-starting external generators and/or Tesla Powerwalls.
All too often I see forum threads (some here, most on different boards) where someone asks a question or seeks advice to improve their design and the respondents don't answer the question. Instead the respondents seek to change the whole plan, causing the asker to wander away in frustration. I tried very hard not to do that to you. To be honest, I had a good time working through some of these challenges.