Hello and thank you for your message. Sorry for my late reply (have to set up notifications for this forum)
1.
here you can see the rows that are created in the table: https://github.com/stefan-klaes/simplest-analytics-wordpress-plugin/blob/main/simplest-analytics/includes/class-activator.php
Every page load will save one row in the database. E.g. 1 user visits 100 pages = 100 rows or 50 users with 2 avg page views = 100 rows. If you use also click tracking it will also create one row per measured click on defined elements.
calculating the kilobytes is not that easy. I would guess 1000 rows will be around 400 kilobytes.
my plugin provides an easy solution to delete old rows in case you want to keep it small. If you have a website with high traffic it could make sense to calculate it more in detail. For super high traffic it could male sense to use external services. For smaller/normal websites this should not be a lot of data.
2.
Yes, you can use caching plugins. In case you use my plugins click/event tracking it could make sense to clear the cache after adding a new tracking because it will add javascript to the code. Just to make sure there is no old version cached.
If you have further questions please let me know.
I marked this as resolved. In case you have further questions feel free to ask.