A) I am not that sure about the (always?) rounded tops.

Definitely not always.
The *average* major market top is pretty rounded. e.g., the average market return from the average price in the week of an absolute cyclical top in the S&P, to the average price in a later week, is about -8% five months after the peak. But an average can hide a lot of sins. Sometimes the market drops a lot, shortly after a recent top.

There are some big rapid dips shortly after fresh recent highs, but the good news is that they tend to be particularly short lived: 1987 and 2020, for example, so it's arguably best to simply ignore those surprise bears. You didn't see it coming, you were long through the drop, but it probably won't last, so just stay long for the bounce. (on average again!) A "no new highs lately" signal will keep you long through the sudden drop, but also long during at least the first part of the strong rebound. After that, it should be pretty obvious you're in a strong market with or without any timing signal.

A tip:
If you do find yourself still long at a big pointy bear market bottom, whether it was a slow predictable bear or a sudden surprise plunge, as soon as you think the bottom is in it's a fabulous time to overweight small caps till about 14 months from the bottom.
e.g., smallest 120 stocks in the VL 1700 set. Not relying on a few lucky picks.
CAGR for 14 months starting Octob 2002: 130% versus 33% for SPY.
CAGR for 14 months starting March 2009: 444% versus 62% for SPY.
CAGR for 14 months starting April 2020: 200% versus 51% for SPY.
To increase the pleasantness, I might limit those 120 to the 60 with the highest ROE, just so it leans to the better quality firms. Not much difference on this measure, but higher on average through the years, better on almost any metric when considering not just the rebounds.

Bookmark this post for next time there's metaphorical blood in the streets and capitulation in every dentist's portfolio : )

Jim