Show the last x log entries when using cursor or dates

Is your feature request related to a problem? Please describe.
I am trying to get the last x lines of logs and then later get the last x lines of logs as long as they are after the initial load cursor. The --after-cursor parameter does what I want until there are more than x lines between commands, then it shows x lines "after the cursor" instead of the last x lines.

journalctl -n 100 --show-cursor

journalctl -n 100 --after-cursor='<cursor>' - shows 100 lines after the cursor

My current workaround (which is much slower when line count gets large):
journalctl --after-cursor='<cursor>' | tail -n 100 - Shows 100 lines from the end but after the cursor

Describe the solution you'd like
I would like to be able to specify to always get the last log lines. Adding an option like --tail makes the most sense to me.
journalctl -n 100 --tail --after-cursor='<cursor>'

This could also apply to --since and --until. If you wanted the last 100 lines from today:
journalctl -n 100 --tail --since='2019-01-01'

Start by reproducing the journalctl commands in the issue, comparing --after-cursor and --since/--until with and without -n. Read the journalctl option handling and retrieval path, then define how a tail-style mode should behave when the range contains more entries than requested. Done means the requested final entries are returned for cursor and date ranges, with coverage for the examples described.