Appropriate HiFi devices for mobile phones-From the designer's point of view, which one is more appropriate, the USB dongles, the Bluetooth Amp or DAC/Amp? (From FiiOJames)

At present, with the development of streaming media, more and more people would like to build their listening systems with smartphones as the core. The main choice is surely TWS true wireless earbuds, which are simple and convenient, and the sound quality is enough to meet the needs of most people. If you have higher requirements for sound quality, you can also consider a system of the FiiO UTWS5 that supports LHDC lossless high-definition Bluetooth with an independent DAC amp, paired with a pair of high-quality earplugs.
Many audiophiles prefer wired headphones though. In this case, USB dongles, Bluetooth DAC/Amps, portable DAC/Amps, and portable music players are all optional solutions. Faced with so many choices, we may be stuck in a dilemma. So from another angle, we would like to discuss how manufacturers consider cost allocation and design priorities within a limited budget in this passage.
1. Under 75 USD budget, USB dongles should be the first choice
USB dongles can be understood as a DAC+ amp circuit module parasitic on the mobile phone. Not only is the circuit simple, but also its small size can save a lot of cost. Because of the simple function, mainstream products usually come with similar solutions, which have low R&D costs.
While at the same price range, it is harder to develop Bluetooth DAC/Amps and portable DAC/Amps, which have extra costs on battery and charging management. Therefore, it is difficult for Bluetooth DAC/Amps and portable DAC/Amps at the same price range to compete with USB dongles in terms of performance and driven capacity.

2. 75~150 USD budget, Bluetooth DAC/Amps should be the first choice
At this price range, because the budget is relatively sufficient, Bluetooth DAC/Amps can be made with richer functions. We can consider it a USB dongle coming with a Bluetooth receiver chip and a battery. USB dongles can only be charged by mobile phones, so they have limited output power. In addition, the distortion of 0.00X can be increased a little bit at most, and it can only achieve some special tuning.
However, Bluetooth DAC/Amps are far more versatile than USB dongles for not only can be connected wirelessly, but also can act as a USB dongle with a built-in battery.
At this price range, if a DAC/Amp comes without Bluetooth, normally it will be designed with higher output power. But audiophiles who consider this price range may pay more attention to portability and functionality. Therefore, it is not so convenient because of its large size and binding needs when used with a mobile phone.

3. 150~300 USD budget, portable DAC/Amps should be the first choice
When it reaches this price range, it is the main battlefield for portable DAC/Amps. Because of the sufficient budget, the cost proportion of the Bluetooth receiving chip is much smaller. At this time, portable DAC/Amps can be farther away out of the league in terms of sound quality thanks to more sufficient power supply and higher driven capacity. While the sound quality of USB dongles is still limited by power supply.

4. Over 300 USD budget, the absolute field of portable DAC/Amps
At this price range, DAC/Amps usually come standard with Bluetooth reception with greater driven capacity, stronger performance, and richer connectors. And a DAC chip model with higher power consumption and better sound quality can be used. Besides, the power of the op-amp will be higher.
Therefore, what is interesting is that in the price range of 75~150 USD, USB dongles, Bluetooth DAC/Amps, and portable DAC/Amps are all compromised in some ways with obvious merits and drawbacks (excluding size and weight). This is what we are considering recently- is it necessary to upgrade the DAC/Amp that was out of stock because of chip shortage, such as the Q1?
PS The opinions mentioned above are personal. Some considerations are based on general situations, excluding individual cases.