The code tends to express notions rather than to give precise definitions as was the practice in the past. Which exact term are you looking toward?
Power is executive, legislative, and judicial. We’d have to know the exact routine tasks you have in mind to evaluate them.
Although such powers are part of his office (ordinary to it), some can be exercized by others by delegation from himself or from the law. Many routine duties are handled by others. The bishop is assisted by his curia. There is another thread on that. See canon 469 +. The vicar general, episcopal vicars, moderator of the curia, the diocesan finance officer, judicial vicar, etc. are examples of this. Some powers are expressly limited to the diocesan bishop though by the law, and these reserved powers are scattered throughout the code.
I would recommend looking at Christus Dominus, ewtn.com/library/COUNCILS/v2bishop.htm and Vatican II, Dogmatic Constitution on the Church, chap. 3. The latter is also somewhere at EWTN.
As well, for an overview, see
Canon 369:A diocese is a portion of the people of God which is entrusted to a bishop for him to shepherd with the cooperation of the presbyterium, so that, adhering to its pastor and gathered by him in the Holy Spirit through the gospel and the Eucharist, it constitutes a particular church in which the one, holy, catholic and apostolic Church of Christ is truly present and operative.
Canon 375:§1. Bishops, who by divine institution succeed to the place of the Apostles through the Holy Spirit who has been given to them, are constituted pastors in the Church, so that they are teachers of doctrine, priests of sacred worship, and ministers of governance. §2. Through episcopal consecration itself, bishops receive with the function of sanctifying also the functions of teaching and governing; by their nature, however, these can only be exercised in hierarchical communion with the head and members of the college.
Canons around 381 and following will provide more.
The Supreme Pontiff can indeed remove a diocesan bishop or restrict his powers of jurisdiction by virtue of his own supreme, full, and immediate power in the Church.
In practice, the Roman curia is a highly collaborative organ in advising the Pontiff, and does have certain powers given in Pastor bonus. Individuals may have been delegated other powers.
As canon 360 indicates: The Supreme Pontiff usually conducts the business of the universal Church by means of the Roman Curia, which fulfills its duty in his name and by his authority for the good and the service of the churches; it consists of the Secretariat of State or the Papal Secretariat, the Council for the Public Affairs of the Church, congregations, tribunals and other institutions, whose structure and competency are defined in special law.
Business in that context would include day to day things as well.