Hello Taxes_for_days,
Welcome back! These are great questions and I appreciate how having all of the options provides a clearer sense of the options available when managing your books. Staying within government guidelines and regulations also ensures that you don't run into any trouble when submitting your taxes. I'm happy to steer you in the right direction to help with this.
As a QuickBooks Team member, I'm able to guide you on the features of the program, but for questions like this, it's better left to the Ontario Government or perhaps even an accountant. From a quick read, I see on the Employer Health Tax page from the Government of Ontario that it mentions making monthly payments, however I encourage you to contact the Ontario Government to learn if there are other options available to you. A more thorough read of the page I linked may even let you know about remittance frequencies, as well as which businesses this applies to, so I recommend taking a moment to go over it.
An accountant may also be able to advise you on this. If you already have someone you're working with, you can even add them as a user to your account via the My Accountant tab. Use the email invite field to bring them on as a user, which gives them access to your account so they can help you directly in your books. That same tab also has the Find a pro to help button, which you can use to search QuickBooks-certified accountants near you.
All the best!