This does depends on what kinds of plants you would like to grow basically.
IMO and from i've learned personally,
For example 2x T8 tube lights are good for low tech level lighting, for plants such as anubias, java ferns, elodea etc
2 x T5 tube lights are good for low to medium level lighting, you will get better plant growth for such plants like cryptocorynes and vallis.
However if you were to have 4x T5 lights or high wattage LEDS then you will be going into high tech territory, for plants like carpet plants, and red or fine leaved plants as general rule.
Do be aware that a lot of LED lights are generally for Marine tank set ups, which are extremely white lights, 9,000k+ which won't do much good for plants really, you will be looking for LED that have output of at least 1w or better yet 3w per LED and 6,500k which is more beneficial for plants.
Avoid cheap LED light units with a few blue LEDS, generally these have less than 0.5w per LED and clustered close together and of no real benefits imho.
Also with high tech set up, you will probably do need a Co2 system, either as pressurised Co2 or liquid Co2, daily dosing of fertilisers, and possibly root tabs for stem/root plants.
In a nutshell, more lights means plants will need more nutrients and co2 to grow well.
I have only just started doing high level plants and still have quite a bit to learn but thoroughly enjoyable.
A lot of this does depends on tank size, depth of water, types of plants, substrate etc etc