With power supply and some storage included in price? And before, or after adding a network interface card for a second port? Regardless, those do look like a nice option if they will accept a NIC card. A bit more CPU on them than an R4S too.
Keep in mind that you either need to use a managed switch (for a router-on-a-stick configuration using VLANs to separate WAN and LAN traffic over the same singular ethernet port) or you need to get an additional ethernet port (e.g. USB3 gigabit ethernet dongle like tp-link's ue-300 to name one with decent reputation around here) or find a way to use the M.2 slot to attach ethernet. Both options will work, but neither comes for free, potentially changing the value comparison with the R4S somewhat.
There's this listing, for example, which includes power supply and 16GB eMMC for $55 shipped. A second NIC will need to be added, though. And the R4S price of $75 is without power supply
Understood, but a USB3 adapter costs about $15, and with the 5070 available for $55 shipped (in the US), it seems to compare quite favorably on price and performance, and at least come close on power usage, to the R4S.
Is there any requirements for the SD cards on R4S? Minimum/recommended size and such?
What about writing the needed files on the SD card? Any requirements for that?
And lastly, what format method is the correct one... NTFS, FAT32, exFAT...?
i use ext4 on mine
The R4S will accept up to 128 GB SD card. I use a 32 GB card on mine, because that capacity is very inexpensive and I do not need more than MB's for my use as a router anyway.
Formatting your card as ext4 is far more flexible if you plan to make full use of the R4S with docker, etc. and want to utilize all the SD card storage. You can also enlarge the ext4 OpenWrt partition to make room for a LOT of packages. Disadvantages of ext4 include: a) every time you upgrade OpenWrt, you will need to manually set up your card partitions again, and b) if you need to reset the R4S, you will lose all your installed OpenWrt packages and have to reinstall them, and OpenWrt if not running a stable release, again.
An advantage of formatting your sd card as squashfs, provided you build your image using the Firmware Selector, is that if you reset the R4S to defaults all your packages that you select to be included with your Firmware Selector image will be retained. The disadvantage of squashfs is that it does not leave you a lot of room to install lots of package and it makes no use of the rest of your SD card.
I use squashfs, because I use the R4S as a basic gateway router and nothing else. I do install a fair number of packages and I still have 86 MB left for more packages. It meets my needs with margin to spare. But I do lay awake at night worrying about all those GB of storage on my SD card going to waste