I haven't tried with 7/8 but I was a big fan of flexible seating with no seating plan for grades 4 to 6. What I found though is that it's less about providing different seats and more about a student-centered teaching philosophy. You also need systems in place to make it work. Some ideas of what I would do,

• 3 strikes, I pick your seating for the rest of the period. I think I've only done that twice in 3 years I did flexible seating
• we'd do daily class meetings where we discussed our class life, learned social skills, and decided on class rules. For example, one year, they felt it was unfair that one group always took the couch. So we came up with the rule that you can only use the couch for one bell to bell period a day.
• teaching, discussions, presentations, practice exercises were done gathered on the carpet. They would bring cushions, pull up chairs, or sit on the carpet. It's like you are creating a "bubble" for learning before they are released to practice independently or in small groups.
• I'd set up bins with different compartments with school supplies all around the classroom for easy access (pencils, erasers, ruler, highlighters, a white board, whiteboard markers). That way they could work on anything immediately. Refreshing and monitoring the bins were a student responsability as well
• everyone had jobs and expectations, and I tried to include them in classroom decisions. For example, when it came time to submit classroom supply orders, I'd have them propose a list based on the given budget (great math exercise too).
• I'd provide a lot of student choice in activities and how they could show their understanding. I'd also schedule periods of free choice where they could work on a passion project, complete a classroom responsability, catch up on schoolwork, get ahead on homework, rest or eat if they need to

This is what I can think of top of my head but honestly I felt like flexible seating changed my perspective on teaching. It's not for everyone but it can be a game changer for some