In regards to smaller [but DENSE] rigs:
While I’m not new to cramming a bunch of PCI / PCIe components, to a single system. But back then, one could arrange the devices [WiFi, soundcard, etc], in such ways to avoid blocking fan(s), should the slots be close. Now with more powerful PCIe components and majority of GPUs being 2+slots tall [and 2+fans] and devices like NVMe trays, being nearly length of a GPU [if not longer, against some GPU iterations].
An ASUS Hyper Card, is planned on being set below the GPU [next and last x16 slot]. Gonna be waiting a while, in scrounging up green, towards a bulk NVMe purchase… Have to entertain a [unwanted] car purchase soon enough
For those that have done a similar predicament → How much concern should I have [thermally], in having such devices, that close in proximity? Any workaround, like blower style [or a single slot GPU], be a more appropriate measure, should thermals be a problem?