The generation of high-performance pulses in the 2 μm wavelength range has been widely considered. A Mamyshev oscillator featuring cascaded spectral broadening and offset spectral filtering is an excellent platform for generating high-energy femtosecond pulses. In order to make up for the shortcomings of complex structure and unsuitability for practical use, in this Letter, we present an experimental investigation of an all-fiber thulium-doped Mamyshev oscillator that enables self-starting operation and generates high-performance pulses. The oscillator emits pulses with energy of up to 7.5 nJ, which can be compressed to 350 fs. Furthermore, we investigate the nonlinear dynamics of the multi-pulse state, such as soliton molecules and high-order harmonic mode-locking. The oscillator generates 130th order harmonic mode-locking that corresponds to the repetition rate of 588 MHz, and the signal-to-noise ratio exceeds 60 dB.