First, there are two programs here that you should understand. The first is VERA, or voluntary early retirement authority. This is the authorization for an agency to offer an early retirement, and sets the conditions for who is eligible, currently at least age 50 with 20 years of service, or any age with 25 years of service. It allows an immediate annuity and continuation of health insurance (note that there are conditions on continuing health coverage, specifically being enrolled in FEHB continuously for 5 years prior to retiring), and you will get the supplement when you do hit your MRA. You won't be offered VERA simply by asking for it, it is a tool for agencies to use for substantial reorganizing of the workforce. There is no "buy out" provision with VERA only.
If you retire early with a deferred retirement (not a VERA retirement), you won't keep health insurance or get the supplement, and if I recall correctly the annuity payments start at age 62. Deferred retirement is worse than early retirement under VERA.
The second program is VSIP, or voluntary separation incentive payments. This is the "buy out" provision, and currently offers a maximum buyout amount of either $25k or $40k, depending on the agency. Again, you probably won't get it simply for asking. The OPM website has more information for both VERA and VSIP. The VSIP payment is taxable.
I am just a little over 2 years away from MRA, and I am ready to go now, but without a VERA I would not be able to continue health insurance. So I am sticking around until MRA, where I will have 32 years of service. So, yeah, I feel that I need to "stick it out" but overall, with a healthy TSP, I am happy to have stayed in federal service.