Many years ago I bought this 127 pieces Drapper set from Amazon:
It was 40€ but poor quality, several pieces have rusted or broken even though I've never wet them nor applied too much force.
It has many redundant tips, for example, if you have tamper proof version you don't need the regular one, or it has the same bit with different lengths.
And most importantly, there is always some bit that you need that it is not there or it has few sizes of some rare shapes.
Do you know any better set?
More important than the total number of pieces is the number of different screws is able to open.
tri-winged, torq-set, bristol, tri-groove, tp3, pentalobe, xzn, spanner, torx plus, motorq, hexstix, outlaw unigrip, loctec, minus, plus, tri-groove...
And other stranger.
Sometimes I need to build my own bit.
having something like this universal wrench but smaller would also be nice:
I'm sorry I don't know how to add pictures here.
The set you purchased looks pretty comprehensive. But, I doubt any single set would ever meet everyone's needs. You might be better served by purchasing several sets, then making a custom solution based on your needs.
Bits come in different lengths because sometimes the only way to gain access is with the proper length bit.
Security bits are often drilled to fit around a protruding post. This feature makes them weaker, so I would only use a security bit on the security head. Non-security heads should be driver with a non-security driver.
Quality is very important, but contributes a lot to the cost. The two things you'll gain from higher price bits is given to you in better materials. The bits will not wear out as rapidly, and they will be able to survive higher torque values. Corrosion will largely affect cheap and expensive bits equally, I'd suggest a light coating of oil or wax.
The quality is low, but these bits are smaller in diameter than a standard 1/4" bit, sometimes they are the only bits that will work.
Wiha makes some great bit sets and drivers, as does Wera.
Wiha also has some great sets of precision drivers. You'll pay for the quality, but they are great tools. You can make a holder like this when you have enough:
Wiha Precision Screwdriver Stand