As JDRoberts already said, there are so many options and no right answer here.
However, I can give you my experience with a few products.
Motion and Door Window Sensors. I use the cheap Xiaomi products. The device handlers have come a long way in the last year and they have become very reliable for me. Make sure you have the SmartThings v2 hub though as they seem to work best with that one. Also there is a 32 device zigbee limit on the SmartThings hub so if you get more than that you have to start looking into repeaters. They are cheap and a good point to jump in and play with.
For camera’s I have the Ring floodlight cam outside and a couple Wyze cameras for inside. None have direct SmartThings integration though but the Wyze cam’s were so cheap it was worth it. The v2 of them is suppose to add IFTTT integration which you can that tie into SmartThings but no word on when yet. Also you may have to put in a little work to get them from the states.
For my lights, I’ve gone with all switches. I’m not the only one in the house and wanted a physical switch everywhere that still worked. Installation is a bit more complicated and you need to worry about things like neutral switches but its all worth it. I do have some bulbs in my basement, I set those up to automatically turn on and off when I turn on the basement stair light. Its an unfinished basement and I like it all lit up when I go down there.
No idea when it comes to vacuums. Read a lot of good things about the Xiaomi vacuum’s but also very hesitant about ordering something that expensive from china. If it breaks will warranty be an issue? I haven’t looked too deep into it though.