Will Monterey slow down my Mac Air 2017

I was running Catalina on a 2019 MacBook Pro (16 GB RAM) and on a 2013 MacBook Air (8 GB RAM). Both have plenty of free disk space (600-700 GB free space).

I upgraded the 2019 MacBook Pro to Monterey and it seems a little more responsive (faster) than it was under Catalina.

I upgraded the 2013 MacBook Air to Big Sur (that is as far as it can go) and it remains quite responsive. Dialabrain indicates that Monterey is supposed to be a bit faster than Big Sur. That makes sense because Monterey implemented some improvements in efficiency for the utilization of APFS SSD drives, memory management, among other things.

Based on this, I expect your 2017 MacBook Air will be fine under Monterey, but make sure it has at least 8 GB memory (16 GB is better) and plenty of free disk space. When the Mac uses up most of its memory it starts to page more to disk, and if there is not plenty of free disk space, it can slow down to almost a crawl.

Empty Space Requirements  >> If upgrading from macOS Sierra or later, your Mac needs 26GB of available storage to upgrade. If upgrading from an earlier release, your Mac needs up to 44GB of available storage. 

Empty Space afterwards - it is suggested to keep at least 15% to 20% of the Drive Total Capacity as Empty Space for good operations of the computer and for additional updates to Monterey to download, expand and install.

Do you have a Rescue Plan In-Place. This comprises having 3 Backups using 2 methods and 1 Off Site incase of Theft, Loss or Natural Disasters. A Time Machine Backup  is very useful and can be used to Revert to Previous Working macOS. 

For addition purposes - two Tested Bootable Clones each to separate external drives. This is insurance incase the upgrades goes sideways. At least one Tested Clone and / or Time Machine Backup should be Off - Site

In theory Monterey is supposed to be slightly faster than Big Sur. Personally I haven't noticed a difference.

It didn't slow my late 2015 21.5" iMac or my 2016 13" MacBook Pro no touch.