The Constitution of Pennsylvania of 1776 established the offices of a President and Vice President to be elected by the General Assembly and Supreme Executive Council out of the Council members.
Sect. 3. The supreme executive power shall be vested in a president and council.
Although it was not precisely spelled out, the President and/or Vice President were entitled to preside at the meetings of the Supreme Executive Council which could not achieve a quorum should President or Vice President fail to attend:
Sect. 20. The president, and in his absence the vice-president, with the council, five of whom shall be a quorum, shall have power to appoint and commissionate judges, naval officers, judge of the admiralty, attorney general and all other officers, civil and military, except such as are chosen by the general assembly or the people, agreeable to this frame of government, and the laws that may be made hereafter; and shall supply every vacancy in any office, occasioned by death, resignation, removal or disqualification, until the office can be filled in the time and manner directed by law or this constitution.
In all other articles, the Constitution referred to the chief executive officer as President, who was also recognised as Commander-in-Chief:
Sect. 20 <...> The president shall be commander in chief of the forces of the state, but shall not command in person, except advised thereto by the council, and then only so long as they shall approve thereof.
A joint session of the General Assembly and Supreme Executive Council on 5 Mar 1777 adopted "by a very great majority" a resolution to proclaim Thomas Wharton, Jr., "in the stile and title of His excellency the president of the supreme executive council of the commonwealth of Pennsylvania, captain-general and commander in chief in and over the same." [Journals of the House of Representatives, 124] In all further elections, it became customary to issue a similar proclamation where the elected official was declared "President of the said Supreme Executive Council" and proclaimed "Captain General & Commander-in-Chief in & over the Commonwelath of Pennsylvania" [Pennsylvania Archives - Colonial Records, 11:634, 13:113, 13:414, 14:565, 15:584]
The documents issued under the authority of President and the Supreme Executive Council were normally titled "By the Supreme Executive Council of the Commonwealth of Pennsylvania", "By the President (Vice President) and Supreme Executive Council of the Commonwealth of Pennsylvania", "By President, & Council of the Commonwealth of Pennsylvania", etc. [see Pennsylvania Archives - Series 4, vol. 3].