don't get too hung up on 'junior' as a grade - different studios use different words and have different criteria for reaching different grades. If the pay fits and you like the sound of a job, take it WRT tech-art Specialising in anything is probably unwise at a junior-ish level. It's not the same as being a junior artist…
The tech artists in most demand or those who have a degree in Computer Science/Engineering (including Computer Graphics classes) but also have taken 3d art classes and have made indie/hobby games in their spare time. Of course, people like that are qualified to be pure engineers, especially graphics engineers, who get paid…