Best shoes/boots for RS Best of Scotland tour, June weather?

I spent 10 days in Scotland in April/May 2023. I wore hiking boots the entire time and they were fantastic, I wouldn't do anything different. I wore the Merrell Moab waterproof mid which are a mix of leather & canvas and are very comfortable. I would not recommend stiff, heavy mountaineering boots. But the Merrell Moabs were comfortable all day long on streets, cobblestones and endless castle stairs. The waterproofing is not Gore-Tex but it was plenty good enough for Scottish rain and puddles. Merrell also makes a low-top version.

You might be walking around standing stones or other areas with soft soil that may be wet. Highly recommend waterproof shoes. I went to Scotland in the summer of 2024 and bought some waterproof
On cloud sneakers that were fine. Weather in Scotland is highly changeable and there is a lot of mist )rain/wetness. Also recommend a raincoat, and a rain hat if you wear glasses.

Your friend should take both of his friends' advice: where comfortable shoes; if they're hiking boots, all the better. As others have said, they don't have to be hard-core boots. He certainly shouldn't wear brand-new or otherwise uncomfortable shoes, no matter what type.

I live in Skye and wear Merrell walking trainers or lightweight Merrell hiking boots pretty much day in day out. The only exception would be to go out for a posh dinner, or in the absolute height of summer when I might wear sturdy sandals. Wear something comfy and waterproof and you'll be fine.

I've been on this tour and in no instance did we need full on hiking boots. There was never time to do an actual hike. We DID need waterproof shoes (had an especially wet day on the Mull->Iona day!) but would have been fine with low cut waterproof athletic shoes.