Marcus already identified that you are confusing bandwidth and frequency, which are of course related but mean different things. In short, people refer signals as having some bandwidth centered around a carrier frequency. The carrier frequency could very well be zero, making it a baseband signal.
Assuming you're comfortable with that, let's answer the last part of your question:
Would you have other effects/consequences regarding the radar bandwidth choice which could be relevant? If you would have some helpful external resources to consult, that would be welcome too.
Regulatory and Spectrum Management
Countries and their respective governing bodies usually have regulations that dictate what frequencies and bandwidths radar and communication systems can operate on. These regulations are meant to mitigate the effects of interference between systems. Many times, military applications take priority and exclusively take up certain frequency bands.
In microwave and antenna engineering, there are special relationships that involve the wavelength $\lambda$ in use. For example, a dipole antenna whose length is $\lambda/2$ will have an antenna gain of approximately 2.15 dBi. So depending on the frequency of choice, this antenna can be physically large.
At a frequency of 100 MHz, the wavelength is 3 meters. If you wanted to achieve the 2.15 dBi gain, the antenna would need to be 1.5 meters long. Contrast this to achieving this at 10 GHz, where the antenna need only be 15 cm long.
These types of relationships apply to the entire RF chain, effecting the size of waveguides, circulators, isolators, quater-wave transformers, etc. Many times this is why systems at lower operating frequencies are physically very large.
Depending on the application, you may need to consider certain frequencies, such as for atmospheric absorption properties. In other applications, the sizes required to achieve certain performance metrics (like antenna gain), immediately eliminates an entire set of frequencies from use. An example being airborne radars, that must fit within tight space constraints.
In many radar and communication systems, being able to observe a large bandwidth is desirable. With large bandwidths, one can achieve higher data transfer rates, accommodate multiple signals simultaneously, and in radar systems, achieve good range resolution.
However achieving larger and larger bandwidths becomes more difficult. For starters, the RF hardware must be able to accomodate it, and doing so is expensive and some performance trades must be made. In addition, high sampling rates are required from analog-to-digital (ADC) converters, which can be prohibitively expensive. Observing large bandwidths also increases the probability of encountering interference.
Having too large of a bandwidth violates some assumptions made in microwave engineering. An example being how an antenna is designed, usually around a single frequency. Transmitting a high bandwidth signal now changes the antenna pattern significantly as the signal is being sent out, which is usually undesirable. There are high bandwidth antennas that can handle this, but are usually more exotic and expensive.
There are many more reasons that determine one's choice of bandwidth/frequency. There are many free online sources of information, such as microwaves101.com, RFCafe.com, Radartutorial.eu, and university sites.