The percentage of energy coming from aerobic production changes as exercise intensity increases. So, yes, as you ride faster you will increase the percentage of energy that comes from glycogen and decrease the percentage that comes from fat and oxygen.
Whether or not you will actually deplete your glycogen stores within the muscles (i.e. "bonk") depends on how well your muscles were stored with glycogen before the ride, how fast you are riding and how well you are refueling during the ride.
Also know that higher-intensity exercise burns more calories per hour and does rev-up your metabolic engine. Increasing your base metabolic rate is a good thing.
Not bonking and not over-consuming calories during a ride takes some experience and the ability to increase or decrease calories on the fly, or by plan. This means increasing or decreasing your ride fuel rate depending on the type of ride you're doing, the condition of your fuel stores coming into the ride and whether or not you are trying to lose weight.
You might fuel at a rate of 200 calories per hour for an easy ride, but need more like 400 per hour for a very long day in the saddle or a ride with some intensity blended into the mix.
•Safe and reasonable weight loss at 1.5 to 2.0 pounds per week.
The range you mention is safe, but know that two pounds per week means 2 x 3,600 calories per pound = 7,200 calories less per week than you are now consuming to keep your current weight.
Averaging that out per day means a deficit of around 1,000 calories per day. That deficit is really tough to do in a normal training situation (not a training camp or a bike tour) while keeping your performance from dipping.
When most people begin a weight loss program, some of the battle is managing hunger (or imagined hunger) and replacing old, bad habits with new ones. If you are able to drop some weight and not decrease performance, let us know how it goes, what you did and if you used any of these tips.