my older Base Station/TC
Sorry but you need to spell it out..
Is this one product.. or two?
I need the exact model.. Assuming it is not the tower AC version then on the base (first line of moulded txt in the rubber.. or on the paper label) tell me the A1xxx number.
The actual speed will depend on a number of factors but you should always run a test with ethernet first.. wireless off. If the speed is slow over ethernet that indicates a WAN issue..
** Did you try my swap WAN to LAN trick with bridged ABS**
See point 5 above.. this can fix a lot of problems.
If you have slow speed over 2.4ghz that is because Apple deliberately restrict it. You will max out around 60Mbps in any older ABS/TC using 2.4ghz.. because Apple restricted wireless.
You must use 5ghz.. which means using a different wireless name for 5ghz..
Then you must check the link speed in the computer.. hold down option key and click the wireless fan.

This is with AC wireless.. so I am showing off a bit..
Look at the Tx rate.. it must exceed the throughput by x3 .. ie to get 150Mbps actual speed.. you need a wireless link of 450Mbps or near to.
My second - shorter question is, now that i have a green light on my base station and can see my time capsule - does that mean it will still work as hub for my printer and other usb storage disks - or is it better to turn the wifi signal off to lessen interference?
There are enough wireless channels to use 3 wifi routers in close proximity to each other. So there is no need to turn off wifi in the TC.
It will act as hub for printer and usb storage etc.. but network reliability maybe poor if you link to the main router instead of the TC direct.
Sometimes wireless does cause issues if the auto channels don't work..
Open wireless diagnostics on your computer.
It is in the screenshot I posted.
Open the scan (wireless diagnostics themselves are pretty useless).

In the scan make sure the channels are widely separated or the power levels (RSSI) are very largely differences.

Your current connection will show up in bold.. and it should show markedly better signal and hopefully a wide gap with other wireless channels being used.
Post your scan if you need help to understand it.