If I understand you right, you were asking can you play only small sector 1-2 pockets or you have to play wide as half of the wheel.
Advantage play is not a miracle. Casino has advantage 2.7%
If with some kind of advantage play you have ~30% advantage over casino do you understand what does it mean? Probably you do but still let me explain some points.
2.7 % is not much.
You may have $1000 with you, you come to casino and play $100 per spin.
To lose $1000 you would need to place on table about $37,000
If you are playing by $100 per spin it should last you 37000/100= 370 spins.
But most likely it will not happen. Reason for that is that much earlier you may hit series of bad losing strikes and your $1000 will be gone much sooner.
For example 1
0 spins you place $100 on number 5 and in 10 spins number 5 doesn't come. After 10 spins you are out of game, maybe next few spins 5 may come, it would give you $3,500 to play additional 35 spins but you did not have any more money to play.
If you were placing your $100 across 18 pockets it wouldn't be easy to lose 10 spins in a row. If you were distributing your $100 across 5 pockets most likely in 10 spins you will get one or 2 hits on your numbers and win…etc
When you play with an advantage even that may be 30% over the house almost same principle applies.If casino removes 10 pockets from wheel and next 10 spin you try to predict single number you still have greater chance to not get it, even 10 pockets from wheel is removed. If you distribute your $100 across all remaining 27 pockets you will profit every time ~30% of your invested money.
When you play 100 spins without advantage on average you will get 2.7 hits.
If you play good wheel with ~30% advantage you may get 3.7 hits.
One hit extra per 100 spins.
You may play $10 each spin, after 100 spins in average you will profit one win $350. Sure you can play $100 per spin and in such case after 100 spins you should profit $3,500.
But playing $100 on single number is unstable. Very easy you can get 20 spins without win, it can happen even 50 spins without win and in such case you may lose $5,000. Of course sometimes it may happen that in 10 spins you get 2 or 3 hits. There is not much of balance when playing just one pocket.
So how it is done?You play more pockets, but all pockets played are in area where the advantage is.
So let's say you distribute your $100 across 5 pockets ($20 per number)
Now each of 5 pockets produces you one extra hit per 100 spins.
Therefore after 100 spins you should win 5 x 1 hit x (35x$20)=5x $700 =$3,500
Notice that it is still same amount of money, as if you were placing $100 on a single number. This time by playing 5 pockets you are more protected form bad luck patterns.
Next question may be, if I can cover 15 pockets should I do it?
NO, perhaps on some wheels it may still be ok but in most cases it wouldn't be good solution.
Have a look this graph. It is typical advantage marked in green.

Look at position 20 to 25, if you play there you would have nice advantage of about 30%.
In this particular case even if you play 15 pockets (15-30 position) you will be ok but advantage would drop to about 15-20%.
It is not bad but
you also need to consider that selecting where to play after analyzing data and during the game where you have a single chance to do it the best is not the same. So by playing 5-7 pockets even if we did not pick the best position where to play we would still be in advantage area while if we play 15 pockets, many pockets we cover may be where the advantage is negative.
Advantage play is so much more then just increasing chances by VB or roulette computers.
I do not go around advertising and trying to convince average Joe; hey give me $2000 and I will send you money printing machine.
So guys please be careful and do your homework before deciding to purchase any roulette computer.
I am trying to be fair to all as much as I can be. I understand that for most people is imposable to know what the roulette computer or advantage play is until they try it.
Often on internet everything is misrepresented and people get wrong ideas.