There is just this question:
Anybody have any experience of 24V LED strips with 3014 LEDs and how they compare to 3528 or 5050 based products?
No, but ...
You can look up the specs, and assuming they are a similar colour temperature (actually spectrum as they don't give "broadband" white light) is similar then you can directly compare the lumens/LED - and then work out the lumens/m taking into account how many LEDs there are. As a first approximation, you can directly compare the W/m of the different strips. It's not quite accurate as the power lost in the series resistor doesn't make light - and that's going to differ between 12V and 24V strips.
It really doesn't matter (light wise) whether the assembly is 12V or 24V - that just determines how many LEDs in a group. Typically you'll find 3 LEDs per group for 12V, and 5 LEDs per group for 24V (dunno why they didn't use 6 - at least in the strips I've seen). In both cases the LEDs will be in series, with a current limiting resistor - or less common, a small regulator chip. The ones with a regulator chip tend to state that they are regulated, or give an operating voltage range.
If you want to dim them (BAS - take note here !), then that is best done by controlling the current. The brightness is not that linear with voltage - but it is near enough linear with current. But where LEDs are used built into stuff with a dimming function, that's more often done by PWM* - and most LED driver ICs have a PWM dimmer function. Also, most "quality" LED setups are current controlled - at least one of the assemblies someone posted a link to stated it was 350mA. That means it's designed to have 350mA through it, and the voltage will be what you happen to get (which varies with temperature amongst other things). Never ever try to drive a "naked" LED from a voltage source - the current will be nearly uncontrollable and you'll destroy it unless the power supply is too limited in current. It is vital to understand what you are buying
Just because (as in the case of the aforementioned module) it gives an operating voltage range (eg 34 to 36V), that does not necessarily mean that you can control it with a voltage source.
A DIY way to do it with the 12V stick on strips is to have a power supply with a variable current limit. Set the max voltage to 12V (so you can't overdo it and blow the LEDs, and then vary the current limit between zero and whatever the length of strip you use pulls at 12V. While I was experimenting at work, I just used a bench power supply set to 12V and fiddled with the current limit.
* Pulse Width Modulation. The power is either on or off - but the duty cycle is varied. If it's one for 25 of the time and off for 75%, then the output will be 25%.
As an aside, one of the reasons for using PWM is that colour varies with current - so dimming by varying current can cause colour changes. Since PWM drives are always either 100% (full power, so one colour) or 0% (off, no not making light), that means you get consistent colour while dimming.
