For me recently i bought a range of mobo's with differing amd chipset boards to play with inclduing B450 (yuk) B550 (better) X570 (building a gaming pc with that bad ass) because its been a good long while since i built a new pc or rig having skipped Ryzen gen 1 & 2 lol ihave goe from A series APU straight to Zen 2 and have had to learn about m2 issues and ryzen pci-e allocations etc etc as all new to me but this HW should last a few years now.

As far as fire goes when using splitters its an odd thing to suggest imo as there is no real power in a splitter with it being all signal so fire is unlikely going to be caused by a pci-e splitter where powered risers are properly deployed like one string to each riser. I have known failed splitters as they do get hot so keep spares about as you do thou the Borg surely wouldn't approve of such redundancy haha. But bear in mind my rig also heats the house in entierrity so down time is also cold time and winter is coming....

I used a splitter because with an M2 NVME installed it cut down available lanes and solved the problem quickly avoiding any more down time but the M2 NVME makes compiling drivers so quick i can do in an hour what used to take all day when testing driver versions....

In a production environment a better solution is to buy dedicated mining hardware and I fancy a 8+ GPU rig now so looking about at those for a "play" but still have spare slot in the splitter and could swop out the M2 NVME and replace with a USB riser to attempt 8GPU on this consumer level mobo might even get 9 out of it, perhaps in time and if it gets properly cold this winter.... However i am conscious of the philosophy "if it isnt broke then dont fix it".