you can surely do this in Reaper. The workflow depends on your specific needs and aims. You could simply record the entire content of side A as a single file, then flip the sides and start a second recording pass for side B. As the recording format, you may wanna choose between Wave, MP3 or a losslessly compressed format like FLAC or WavPack.
Instead of recording entire sides of the cassette you may prefer to record each track separately into its own file (in the desired format). If you plan to do further editing or sound processing, you should choose one of the lossless recording formats like Wave, AIFF, FLAC, WavPack. This will ensure that no sonic details will get lost during post-processing. You can still render the processed file(s) into a lossy format, if desired, to save disk space or to make them compatible with a specific media player or device. I find WavPack very convenient to archive important material at full 24 bit capturing resolution. For less critical material I'd capture it as Wave but would later convert it to high-bitrate AAC/M4A (using fre:ac). AAC/M4A seems to suffer from less audible artifacts at a given compression rate.
To streamline the process, I'd capture both sides of the cassette entirely as one Wave file (so I could do something else during the capture process of each side). Then, I'd slice the captured file(s) into tracks (trimming and fadeing them carefully). I'd then create regions for each separate track and name those regions according to the "Artist - Title" labelling scheme. Finally, I'd use region rendering to consolidate and name all files in one go.
Set your recording levels carefully!
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