MySQL 5.8 utf8mb3 Deprecation

My company's infra team is converting our internal MYSQL databases from 5.7.x to 8.0 since 5.7 is approaching End of Life.  With that comes a somewhat major deprecation of the utf8mb3 charset. We're formulating a plan that includes moving our larger VARCHAR fields to MEDIUMTEXT (and understand the implications with sync'ed records), however I have a few questions about some of the finer details related to Appian.

• utf8mb4 takes up to 4 bytes for storage instead of up to 3.
  • When reading a VARCHAR field, does Appian always see the "maximum" size for a value when handling the 1mb limit? For example, does "asdf" under utf8mb3 count as 4 bytes or 12 bytes, considering that no upper unicode characters are used?
  • When reading a VARCHAR field as part of a!queryRecordType, are there any differences between utf8mb3 and utf8mb4 as it relates to the 4,000 character limit on what's sync'ed into Appian?
• Any tips on successfully converting a VARCHAR database field to MEDIUMTEXT without breaking the record fields?