The routing and firewalling is a bit different in terms of why certain CIDR masks are used. For the router, the /24 suffix is usually defined for itself on the LAN interface to denote the address space it may send route information to, and what addresses are controlled by the device. Almost certainly, (unless using a lower CIDR range and actually handing out /24 blocks to subsequent routers,) you are granting /32 IPv4 addresses to your devices from your router.
For your system firewall, 192.168.1.135/24 is identical to 192.168.1.0/24 as they are the same address space. You’re simply allowing from a subnet of hosts to accept from. Given the /24 mask is 255.255.255.0, it does not matter what the last number of the IPv4 address is, but the lowest possible number to match the mask is standard form. Without knowing what rule(s) specifically is being applied, I couldn’t tell you if your firewall rules are something that would affect hostname resolution of other hosts from your system or not.
Iproute2 definitely does write things a bit compact.
ip address showand shorthands state the routed local address space (192.168.1.x/24) and the actual /32 address (192.168.1.214) you are assigned as one unit. Additionally, it shows the broadcast address for the space. Ironically,ip route showmay genuinely give you less confusing information, clearly splitting the actual route and showing your straight IPv4 address assrc.Typically in firewalling, you’d use /32 to target a singular IPv4 host. This is analogous to using /128 for IPv6 hosts. You can absolutely use /24, /16, /8, or any other mask really if you need to target a range of IP addresses for a rule to apply to. Technically, /32 is a range itself, just with a size of 1. There are CIDR calculators available to play around and see what different CIDR masks actually target.