In vapespeak (rollseyes I canaat believe Iva picked upa tha new vapin' lingua) we talk of atties short for atomisers and tips being the separate but end part that fits onto the atomiser.
Ive had an answer to my 901 query through pm with Imeo.
901 is usually the atty that many have experienced before they come to mods because they are ubiquitous on many of the cheap Chinese e-cigs. Dont let that put you off the 901, however, since it is still the choice for some seasoned vapers. Its really a matter of personal taste. If you get into
vaping you will end up trying them all and find your favourite.
I think youre making the right choice buying a high end mod over low end . If you decide
vaping isnt for you, you wont have any problem selling on either of the devices youre interested in. The other philosophy is that people try the better of the low end devices first. To my mind even the good ones are just too fiddly that many I imagine are put off and dont perservere and are quickly back on the analogs.