Note there are known discrepancies between males and females[0], so treat this anecdata as anecdata.

Recently, my brother--who was vaccinated and had COVID (delta) once before but no booster--visited while he was floridly positive. By floridly positive, I mean he was able to trigger a rapid test.

After 3 days of exposure, both my partner and I developed COVID that was only detectable by PCR.

On day 4, I developed a high fever (102), soar throat, cough, congestion. I was then shedding enough virus to trigger a rapid test. My brothers symptoms resolved, he no longer triggered a rapid test. My partner did not have any symptoms or trigger a rapid test. I took an Advil.

On day 5, my fever continued although more mildly, soar throat, cough, congestion continued. I was still able to trigger a raid test. My partner complained of a scratchy throat but did not trigger a rapid test.

On day 6, I no longer had a fever only a mild sore throat and congestion. I was able to trigger a rapid test. My partner did not have any symptoms or trigger a rapid test.

It's day 7, my symptoms have resolved and I was no longer able to trigger a rapid test. My partner? You guessed it: nada.

Note, my partner continued to cohabit with me through this period as if nothing was different. We shared the same bed, we shared the same cups, she give me kisses--you know everything you're absolutely not supposed to do when you're with someone who has COVID, but she never shed enough virus to trigger a rapid test and never developed symptoms of note.

Conclusion: Boosters appear to reduce or even eliminate COVID symptoms. Boosters also appear to reduce virus shedding as evidenced by the rapid test results.

Disclaimer: There's apparently some risk that the virus mutates in one person and reinfects the other. So maybe don't try this at home?

[0]: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7381128/