Is your grip a genuine Canon or an aftermarket? as some are known to have battery drain issues.
I managed to take over 2600 shots at Flying Legends using 1 original Canon battery & 1 ExPro which still had 50% left - (not using grip)
The reason I asked is that I have just bought a Canon BG-E16...
I've had both, as Geoff said above 80d is better for low light but 7D II has much better auto focus and feels much better to use imo.
If buying new it might be worth waiting to see what Canon release later in the year as its rumoured that a 80d/7D II replacement is on the cards which may have a...
I had an 80d for a couple of years but upgraded to a 7D mkii for the 2018 airshow season and I get on much better with this, I find it easier to handle being larger than the 80d and my keeper rate has increased, the autofocus just seems to stay locked on better with the 7d mkii.
I bought a 100mm filter holder from ebay, decent quality and works well with my Lee Super Stopper.
Just looking into the Cokin Z series myself and will probably end up getting a set of the ND's and the ND Grads to try as I am going to North Yorkshire in Sept and want to experiment with filters.
If I get on ok I may well invest in a set of Lee's.
AI Focus will automatically change the focusing system between One Shot and AI Servo but this is not as good as selecting the correct focus system yourself, so if you're shooting a static subject choose One Shot and if your subject is moving choose AI Servo.
An external hard drive would be the easist way to gain storage space, something like this:
Givi make a specific soft camera bag which fits into their tank bags or tail packs : https://www.givi.co.uk/soft-bags/Others/T508
Personally I put my soft camera bag in my topbox and pad it with my waterproofs.