Keisei Narita to Tokyo Crowded?

Hi! So I'm arriving at Narita (Terminal 1) at 20:30 on a Monday

My question: is the Keisei Main Line (the normal commuter line) bound to Ueno Station too crowded at this hour? I'll be boarding it at around 21:30 - 22:00.

The Skyliner is 2x more expensive and I can't take those buses cause I have 2 pieces of luggage and they explicitly state that you can only board with one piece so yeah

Not crowded at that time of night.

Boarding at Narita you'll get a seat easily and even with luggage it's not a bad way to travel.

Thank you very much!

I can't take those buses

Which bus line are you talking about?

cause I have 2 pieces of luggage and they explicitly state that you can only board with one piece

Well, that is, I suppose, not correct.
It is strongly recommended that you pack lightly, but...,
presumably you misread limitation on the luggage
which can be stored in the trunk of a bus
as limitation on the whole personal luggage.

Your luggage of
one traveling bag to be stored in the trunk
+ one middle-size rucksack to be kept
either at your seat or on the shelf above your seat
is allowed in buses probably on most bus lines for NRT or HND accesses.

- Luggage in Japan
https://www.japan-guide.com/e/e2274.html

the Keisei Main Line (the normal commuter line) bound to Ueno Station

The Keisei station near Ueno Park is Keisei Ueno Station.
(In passenger announcements,
Keisei often omits "Keisei" in this station's name,
so it seems as if this station were Ueno Station.)

Ueno Stations of JR and of subway (Tokyo Metro)
are a little away from Keisei Ueno Station.

Where exactly in Tokyo is your first destination?

I'm arriving at Narita (Terminal 1) at 20:30 on a Monday

During the coming 6 months,
Mondays shown below will be public holidays in Japan.
2018
: September 17, 24; October 8; December 24.
2019
: January 14; February 11.