Keeping Sativas short and fast?

Hi, I'm going to start my first growth and all I have is a 2.5 x 2.5 tent with carbon filter and fan and a 300 watt Led light, organic soil and nutes.

I guess I could fit 3 Autos with no problem but in this case I want to grow Sativas cuz' Sativas is all I care about so maybe it would be recommended to keep 2 at max.
I have a super low consumption so I don't care about yields, I only care about the quality and the Sativa high.

I want to grow Kali Mist and Strawberry Cough, these could take 4 months to harvest and I don't know how explosive the growth could be. I could either try to keep them short some how or let them compete with the light although they could overshadow each other.

Which option is better?

Let them compete for light

or
Keep them short

And if I do keep them short and fast, how do you achieve this? For instance, what if you give them 16/8 photoperiod and then switch to 12/12 after only one month?
Would this trigger flowering while still relatively small? Or they would not flower at all?

If they're autos, they'll start flowering around the 3week to month mark anyhow.

I fim and then lst. Fimming is very controversial on autos, but it's the least stressful tactic next to lst and makes it easier to level the canopy. My 2 cents.

No they are not Autos, they are regular feminized Sativas, I mentioned the Autos because I guess I could fit 3 in them with no problems but in this case I want to fit 2 regular Sativas in that space and so it could present problems, plus I want to be able to harvest them fast.

i recommend something along these lines this is a 4x4 with more plants but is easily scaled down

LST + SCROG FOR SUPPORT since you're not vegging for a long time to strengthen stems

-also if the funds are there i might recommend a 600 watt - 700 watt mars hydro light which has that 2.5x2.5 light foot print that you are looking for. they should cost you 125-175 or so or another 300 watt could work depending on your plan.

And what can you tell me about this:

And if I do keep them short and fast, how do you achieve this? For instance, what if you give them 16/8 photoperiod and then switch to 12/12 after only one month?
Would this trigger flowering while still relatively small? Or they would not flower at all?

How long would you keep them in growing phase? How fast can I harvest if I do this? 2-3 months max from seed to harvest instead of 4 months?

If you veg for a month, that's usually long enough for sexual maturity.

However, unless you get fast flowering genetics, you're looking at a 10-16 week flowering period.

As for training them, you can run a scrog as suggested or fim and supercrop them, or top and supercrop, etc. Possibilities are endless. Just keep your canopy flat and circulation moving and it'll all pan out in the end.

In other words, vegging for 1 month won't make much of a difference if they have a 16 week flowering period, right?

In the timeframe you want... No.

They do make some fast flowering sativas though. Pure sativas are still going to have a looong flowering period, but sativa dom hybrids have come a long way. Seems to help with the stretch too.

All in all, 1 month is a solid veg time. You can go longer if you like. I wouldn't recommend much less. Just check some sativa grow journals for banks that honor the sativa genetics that flower in 9-10 weeks.