tonearms, straight and curvy

Which straight tonearms do you mean? A linear tracking type? 

Apart from the linear tracking type tonearms i know only one straight arm (Viv Lab) for high-end market. 

The rest of the arms with straight armtube have an offset angle on the headshell anyway. 

No difference for the cartridge. Straight or S shaped - the arm connects the pivot point to the cartridge. The length of the arm or distance of cartridge to pivot point is a bigger factor. The S shape may have an advantage in slightly reduced LF vibration - the bends at 1/5 and 2/3  of length will reduce low frequency vibration along the entire length - a kind of filter if you will. 

So the "Technics" curve allows for a "straight-on" attachment of the headshell, whereas straight arms require the headshell offset?  Do all arms with a collet attached/removeable headshell need to be S-shaped, in order to accommodate that feature?  

Ideally, you want headhsell offset; the S-curve provides the offset so that the headshell can remain straight. Make sense? Arms that are not S-shaped will need headshells that incorporate the offset at the collet.

So the "Technics" curve allows for a "straight-on" attachment of the headshell, whereas straight arms require the headshell offset?

Ok, let me show you my Reed 3P tonearm.
The arm wand is straight, but there is an offset angle on the platform where the cartridge is mounted.

Do all arms with a collet attached/removeable headshell need to be S-shaped, in order to accommodate that feature?

No, but the headshell for straigh arm is different from the headshell for S or J shaped arm. They are not compatible on one arm.


P.S. This is the only pivoted straight tonearm with straight headshell to mount a cartridge with no offset. You can read more about it. Very strange concept.

Linear tracking tonearm is straight, but completely different from conventionel pivoted arms as you can see.