You're making it too complicated. There is no perfect light but many great choices. Pick one and chances are that you will be satisfied with it. We are living in a great time for bicycle lights with all of the advancements in LEDs. For about $100, you can buy a headlight that surpasses what you could buy for $500 or more just a few years ago. I've owned several bike lights over the past 5-10 years, but the $100 Light & Motion Urban 500 (now 550) surpasses any of the previous lights that I owned -- some costing more money and some less. It puts out all of the light I need (not even running on high beam), is simple to recharge, has good run times, is very light weight, and extremely easy to put on and take off. Lezyne, Nightrider, Cygolite and other manufacturers sell comparable lights at similar price points.
Same thing goes with taillights. Since they are generally less expensive, I use several taillights -- Planet Bike Superflash, Radbot Danger Zone and Dinotte 140. The Dinotte puts everything else to shame but requires a separate battery back that needs charging more often and can be hard to mount. The Radbot is brighter than the Superflash but uses up batteries much quicker. The Superflash lasts forever on batteries and puts out a decent amount of light. As cheap as it is, I have two of them.
Regarding panniers, I struggled with the same issue. However, after reading many reviews, it seemed like Ortliebs consistently had the highest ratings from users. They were priced competitively when buying on-line, available in many colors, highly waterproof and simple to install and remove. I ended up buying front and rear Classic Rollers and have not regretted the choice.