Regarding Magitek:

I've long since given up trying to work out the limitations and perks of magitek at this point. There isn't much rhyme or reason to it beyond 'rule of cool' being put into play. It used to be that all magitek had a certain style to it clearly influenced by FFVI in particular - with some additional elements weaved in from time to time from FFXII.

It was specifically Allagan technology that happened to be super advanced and Garlean technology was initially portrayed as being powerful but not quite as powerful or as advanced as what the Allagans brought to the table.

Yet over time, they effectively became one and the same. Werylt gave us artifical Eikons and super advanced robots. Regula was able to use his trusty blade to summon forth a ceruleum familiar in the form of a proud tiger. There's many other specific examples I could draw upon, but basically...magitek is very, very different now to how it happened to be during the days of ARR.