fq_codel should be fine on any hardware that's still operational and has enough RAM to run a currently-maintained Linux-based OS (eg. OpenWRT). It's specifically the traffic shaping (rate limiting) that tends to hit CPU limits on consumer hardware. CAKE includes a traffic shaper; fq_codel doesn't and usually needs to be paired with a separate traffic shaper.
If you have an older, slower router in your network that is not acting as your gateway router and does not need to compensate for bufferbloat in somebody else's device (eg. you're using it as a secondary WiFi access point), then you should almost always use fq_codel on that device's network interfaces.
Some devices like some cable modems have even more drastically anemic CPUs because the CPU was never intended to be part of the data plane and most traffic is supposed to be offloaded to special-purpose hardware. Those may be genuinely unable to even handle CoDel, and are a big part of the reason why DOCSIS 3.1 invented PIE AQM rather than adopting CoDel as the standard AQM.
If you have an older, slower router in your network that is not acting as your gateway router and does not need to compensate for bufferbloat in somebody else's device (eg. you're using it as a secondary WiFi access point), then you should almost always use fq_codel on that device's network interfaces.
Some devices like some cable modems have even more drastically anemic CPUs because the CPU was never intended to be part of the data plane and most traffic is supposed to be offloaded to special-purpose hardware. Those may be genuinely unable to even handle CoDel, and are a big part of the reason why DOCSIS 3.1 invented PIE AQM rather than adopting CoDel as the standard AQM.