As far as playing Marengo the current issue (125) of Wargames Soldiers and Strategy magazine is themed around Napoleon's rise to power and has articles for a couple of options for playing this campaign. One is a series of three scenarios focussed on Victor's spirited defence of the Fontanone and Marengo against escalating attacks. The article provides stats for Black Powder but the author also recommends General de Brigade.

The other is a relatively common one, a map campaign covering the whole region from the point at which Napoleon marches over the Alps. The Italian campaign of 1800 has got a lot going for it for wargamers, particularly beginners, being geographically and temporally restrained and something great that can be achieved after simply painting a bunch of French and Austrians. Excellent for smaller miniatures scale wargamers. It really suits something umpire managed with a lot of fog of war.
For those living under a rock, Little Wars TV did a great episode on the campaign played out as a big club game with a relatively fast play system, Snappy Nappy.
https://www.youtube.com/watch?v=zbh4G5RUqbY
https://www.littlewarstv.com/members-only/play-the-marengo-scenario?view=full

For gamers curious about board wargames, Triomphe à Marengo is a less conventional block wargame with some good thought behind it and sincere fans here and across the internet. It's certainly something I'll be looking into myself.