Essentially they are doing the same thing but just loaded in a slightly difference manner. I'm not expert but AFAIK cron.daily/hourly does not load any environment variables; whereas crontab uses the environment of the user that it runs from.

So as a general rule, so long as the user the crontab is set up with has the required level of access (root for a TKLBAM job) then a cron.hourly/daily job should be fine as a crontab job; whereas if a job was originally set up to use crontab, it may not work as expected as a cron.daily/hourly job...

But TBH I'm not 100% sure. Why not have a play and see what works best for you?

Keep in mind too that if you are making the incremental backups more regular you'll probably also want to make the full backups more regular too. The longer the incremental backup chain gets, the more "fragile" it becomes.

Regarding the format, I'm not familiar enough to give you any OTTOMH guidance so I suggest that you have a read of some docs. Google turned up this page. It's actually for Ubuntu but Turnkey is Debian based which is what Ubuntu is also based on so should be near enough IMO...

THat sounds totally reasonable to me. Please post and let us know how it goes.