Thete are really just 3 grades and many people get stuck in the second for a long time now and do fine. Having direct reports or gts can move you up faster to the third but it isn't some huge windfall.
Having gts or reports also pretty much locks you into equity and bonus annually.
Job grades are nonsense and the pay ranges within them are enormous to the point where there is very significant overlap with the job grades above and below them so the company can pay you whatever they want at any stage in your career. The whole concept prevents people from being paid appropriately because your actual job title doesn't change, so HR never evaluates you appropriately compared to the market. It's a deeply broken system that the company refuses to fix.
At any other company, JG 26=Eng I.... JG28=Eng III (or "Senior Engineer"). This is on purpose. It's hard to progress beyond that unless you go into leadership or have outstanding accomplishments or go MTS track. The scales overlap like they do anywhere else.
Talk to you direct manager about it. They should be able to go over it all with you. This place isn't well known for big pay, just average pay for the industry, though maybe underpaid for the workload. You're probably not being underpaid compared to your peers at TI on paper. If you want more pay build your skills and move on if you can. If you want work life balance build your skills to where you can handle most of your workload in a reasonable ammount of time and don't take on too many extra tasks. Be strategic in what you take on and what you learn