Is Big Sur 11.5.2 safe to upgrade to?

That should be enough spaced and no reason to disconnect any cables or hardware and always leave the Mac connected to power when doing upgrades. But before doing anything, like noted in your link, have a backup.

Tips How to Upgrade to Big Sur 

There are several points to consider before attempting the upgrade to Big Sur. The most important is Due Diligence on the part of the User and is a Prerequisite for a smooth upgrade.  

Point # 1 - Are there pre-existing Unresolved Software Issues. They should be resolved prior to upgrading - they may carryover to Big Sur making the system unstable / unusable.

Point # 2 - Are there any AntiVirus, Disk Cleaner, Optimizers, Un-installers, etc installed which should be removed as per Developers Instructions. They are useless, unneeded, cause havoc and interfere with the normal operation of the OS and may even Corrupt the OS requiring a Reinstallation. The Built-in Security of Big Sur is all that is required.

Point # 2 A - Commercial VPNs should only be used if Mandated by Corporate Head Office for working remotely. Otherwise - ones Privacy and Security touted by the VPN is suspect.

Point # 3 - What are the System Requirements ie: Empty Space Requirements specific to the Big Sur. Apple stated 35.5 GB Empty Space for Sierra and above. Personally suggest 50 GB Empty Space.

Point # 4 - Does the intended computer qualify for the upgrade.

Point # 5 - Are the installed Applications / Extensions compatible with Big Sur. Check with the Developer for compatible Apps / Extension or do they offer updates. Same goes for Third Party Drivers for Printer, Scanners etc.

Point # 6 - If upgrading from Mojave and earlier versions of macOS - Remember that Big Sur does not support anything 32 bit. These include Applications, Extensions and Drivers for any devices. There is no workaround.

Point # 7 - 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

Point # 8  - To upgrade to Big Sur will requires a quick, stable and reliable Internet Connection - preferred method is via Ethernet Connection. 

If not available and using Wifi - move computer as close to the Access Point / Router and disconnect all other devices connected to Wifi. Want the maximum bandwidth for the computer being upgraded to Big Sur.

Nobody else has your specific combination of apps.

Let that sink in.

Nobody else here has your exact configuration, nor your exact app usage.

Which means—absent an inventory, and arguably not even then as apps can be quite complex and ~nobody uses everything in those apps and it’s rare to see two folks use the same subset of app features—nobody else here can reasonably answer.

If you’re concerned about an upgrade, consider having a spare Mac to test with and as a fallback should this production Mac fail, or clone your environment to a scratch storage device and upgrade that and test that, or generate a complete backup and disconnect that prior to upgrading the internal storage to give you a path to revert.

If correct operations of your Mac and its apps, and if your data is important enough to be asking this question, then having multiple local backups for recovery and disaster recovery is part of operating such an environment. Preferably with a rotating backup disconnected from your Mac, a d possibly stored remotely.

I’ve one old and unsupported app that got buggy a while back, and successive Big Sur upgrades have been addressing some of those issues. So this can go the other way, too.

For your storage question… Apple states ~35 GB or ~45 GB free space is required for an upgrade. I’d plan on having rather more than that available, as running very near or at storage capacity tends to cause various problems and can potentially cause corruptions when something fails to find needed storage.

Local preference is to minimally have ~10% of any macOS volume kept available as free space. And several backups.

Now be careful if it wants to upgrade to 11.6. There are several bugs that people have discovered including myself so that I had to downgrade back to 11.5.2.

Printer queue will not close after printing so printer icon stays in dock (you can manually quit). Cannot play dvd ( cd ok). This may be in region 1 only. Those are two mostly reported.

Dock freezing ?? Interesting - can you elaborate ??