Affirmative. If opkg update && opkg install kmod-blarg (or any package) works without issue, you're fine because opkg found the right one. If you have to resort to the --force... options, then DANGER AHEAD, so best to just upgrade to a new snapshot.
For easy "full upgrades" (i.e., full upgrade of firmware and keep your config), see https://openwrt.org/docs/guide-user/installation/attended.sysupgrade where you'll find a couple of tools that do all the work for you. I prefer CLI, so I use auc described halfway down that page.
If you cannot use auc or LuCI Attended Sysupgrade to build a new image with all your user-installed packages, then you use the https://firmware-selector.openwrt.org/ to do so. Also, add any new packages (click on Customize installed packages...) and add at least auc and your new kmod. If you need to figure out what packages you currently have installed, see this The OpenWrt Firmware Selector - #621 by efahl (any questions, ask them here, that firmware selector thread is getting to be a mess 
).