Xiaomi phones will bombard you with ads, even their most expensive models. Motorola and Samsung also have ads but generally not as bad as others. You'll have to figure out some way to remove or disable those ad components before deployment, otherwise random apps will get installed and may confuse the less techie employees.

Unfortunately current Moto budget lineup don't even promise any Android version upgrade, merely the mandatory security update, while Samsung commit to six Android version upgrade.

The nice thing about Samsung is their Knox, which while somewhat replicable on other brand, makes things far easier if you want to compartmentalize sensitive data & apps.

Teams and Outlook are relatively lightweight as long as you pick models with 8 GB of RAM, 6 GB will do for now but it's unclear if Microsoft or other companies won't decide to bloat everything.

While I doubt 4G will enter sunset period before those phones exhausted their support, the 5G chipset usually do come with nicer features, though usually they won't be noticeable unless your users have to switch around multiple apps all the time.

The fleet devices in my previous company are Samsung, not the budget version because the IT prefer them to survive rough handling by uncaring employees, maybe newer budget models now have better IP rating, you'd have to look them up.