Trust us, we too want the same thing from the routers we're recommending to you. Solid performance with good/great range and streaming.
I would recommend that you read and re-read this thread when you can concentrate more on it. This really isn't that confusing.
I don't think you will find any (single) consumer router that will give you coverage to the pool area at 200' away, but then, I don't know the layout of the home or the construction/materials too.
I'll try to summarize a few things here quickly.
The RT-AC86U is one of the best, most current routers you can buy right now. Significantly better throughput than, and equivalent if not better range, than the RT-AC3100, (the RT-AC88U, equivalent to the RT-AC3100) or the RT-AC5300, in most homes.
What the RT-AC5300 offers is three radios (2.4GHz and 2x 5GHz) that are better suited to a household
with more than 32, 5GHz client devices (and all routers offer
an additional 32, 2.4GHz clients too).
What I can't predict is if the RT-AC86U will outperform in range, in your specific network environment, the class-leading RT-AC3100. Again, I urge you to read the RT-AC3100 Report in my signature below.
As far as AiMesh goes? For some, it is the best thing since sliced bread. For a lot of others here, it could be more descriptively spelled 'AiMess'. I would not recommend it. I personally find it a waste of time right now and far from your requirements. A second, strategically placed wired router in AP mode will be much more reliable.
Another benefit that the RT-AC86U has over the other routers mentioned above is the greater VPN performance it offers in addition to the better handling of 1Gbps ISP connections over any previous models. It is also the newest router (about a year old) of the bunch so it should be supported for the longest time too (and would make a great AP when AX routers hit their stride next year sometime in 2020 and the upgrade 'bug' but may bite).
The accolades and recommendations from me for the routers above come with one condition. RMerlin firmware is a must. Don't let this deter you in any way (but do know that the buggy AiMesh is not included in RMerlin firmware, he wants it to be rock stable too). Simply upgrade the router as you normally would, complete an M&M Config as you should be doing anyway with a router you want stable and with the highest performance possible and then you can just enjoy all the bug squashing and other under the hood improvements RMerlin firmware offers supported Asus routers.
Keep asking questions to clarify anything that is vague. Hope to see you with a solid solution soon.